In the 2010s, up to 2014-2015, the “harem ecchi in magic academy high school” genre was the business. It was everywhere and the source material was often light novels. With Trinity Seven, it started with a fairly appreciated manga and the anime got as popular.
Is there then a chance for a second season?
What happened so far in Trinity Seven

Kasuga Arata and his childhood friend Hijiri Kasuga live peacefully in their small hometown. Their life is turned upside-down when the Black Sun causes the Breakdown Phenomenon, destroying the town and spiriting away its people in the process. Before disappearing, Hijiri entrusts a grimoire to her friend asking it to protect him. Devoured by loneliness and sadness, Arata wishes for his world to be restored to its previous state. The grimoire fulfills his wish by creating an artificial reality where the boy can lead a normal life, with no memory of the real events and no Hijiri.
One day, the mage Lilith Asami is sent by the Royal Biblia Academy to investigate the ruins of a town where a powerful spell has been detected. She then finds Arata and forces him to remember what really happened, which breaks the enchantment. Arata is then confronted with two choices: to die or to hand over his grimoire. He decides to enroll in the magic school Lilith attends to become a mage himself and find a way to bring the townspeople and his cousin. There, he is introduced to six other (female) mages called the Trinity Seven – with Lilith included.
They are the elite of the school and each of them is a master in their own respective field. To much of Arata’s surprise and disbelief, one of the mages looks eerily like Hijiri, yet displays a different personality. Starting his new life surrounded by its seven powerful (and well endowed) friends, Arata will have much to deal with between a secret organization set on destroying the world and the mystery behind the Breakdown Phenomenon.
What is going on with Seven Arc Pictures?

Trinity Seven premiered on October 8, 2014 and ended on December 24, 2014 after 12 episodes. It is written by Hiroyuki Yoshino, directed by Hiroshi Nishikiori with a score composed by the Technoboys Pulcraft Green-Fund.
Trinity Seven offers something interesting to latch on in its first episode storywise. It is nothing revolutionary, but it hints toward what could turn into a fairly decent plot to keep the viewers on the edge. Regrettably, the series fails to actually use the foundation it nicely laid for its world building. The plot development is all over the place, if not nonexistent. It is hard to make sense of what is happening exactly considering the fact that no context and subtext are applied, but terminologies and mechanics are mentioned in passing. It almost feels like the anime is expecting the viewers to already know all the details without any real world building. Meaning that throughout those 12 episodes, the plot and subplots do not deliver anything crunchy enough to feel like we are going somewhere with the scenario.
Trinity Seven is clearly a harem with abundant ecchi and sometimes they do magic tricks. That is really where it shines: when comedy is mixed with lecherous shenanigans. As soon as the show tries to be serious, it loses all its flavour in what could be qualified as “voluntary drunk driving over a cliff”. The anime is entertaining, but only if you are in for some mindless fun.
Thanks to his cast of main characters, the comedy, harem, and ecchi combo work well for Trinity Seven. Arata as the protagonist is a lot of fun to watch. Far from the meek Keitaro from Love Hina, Arata is a certified pervert and proud of his craft. If his hand ends up on a supple breast, he will not back away from the challenge by apologising and blushing. No. Kasuga Arata will seize the matter (literally) and apply considerable pressure (pun intended) on the issue at hand (all the puns). Our protagonist is also pretty competent with magic without being overpowered and boring like Akatsuki (Aesthetica of a Rogue Hero). His interactions with his harem are played out well and the anime makes sure to change the pairings to be able to provide different antics based on the girl. The latter can be done because the female cast comes with different personalities and traits.
Time is actually taken to flesh them out some more which allows diversity in their motivations, ambitions, reasons for their attachment to Arata and reactions to situations (the amusing/sexual ones).The characters are appealing enough for the genre, without reaching Vagabond-level of character growth.
Depending on the angle, the pacing can be seen as terrible or average. If you came here for a story slowly revealing itself by adding new stakes and subplots, it is a miss. As said before, that side of the anime is taken nowhere and the shortness of the series cannot be used as an excuse for the lack of world building. The rhythm of the pace is entirely focused on the characters, mostly the girls. Trinity Seven made sure that the viewers would be able to differentiate them and understand who they were. A decision that serves well the different interactions, but one that turns into a circus when the anime keeps adding new characters in nearly each episode until the last. The focus is then given to the fresh bunch, leaving the old one behind with less screen time. And suddenly, all that build-up loses its interest.
The animation is the biggest flaw in Trinity Seven. The anime uses CGI backgrounds and they simply do not blend well with the 2D characters. The juxtaposition of both is disagreeable and unnatural.The lack in environments is not helping. The character design fares better: the girls all have a contrasting design, with specific physical traits and different shapes. It is not just a festival of big breasts and thick thighs. The animation in itself is terribly limited, using shots with one character, still shots to avoid movement with a crowd and poorly choreographed and oversimplified battles. At the moment, the studio Seven Arcs is working on the coming of age anime Blue Period.
What do we know about Trinity Seven Season 2 so far?

Unfortunately, it looks like a new season is not a priority for the studio right now. Something that fans cannot understand as the anime was pretty popular.
What are fans saying about Trinity Seven Season 2?

Trinity Seven might not look like it , but the anime was actually appreciated upon release. It was ranked 17th out of 18 in the Most Popular Anime in 2014 category on MAL (meaning that were included all the anime from spring/fall/summer/winter 2014), included in the TOP40 on ANN for the same category in a list with around 200 different anime and has positive stats on Anilist. It made new fans, and a lot of people liked the anime.
Therefore, the fandom is not huge, but it has a nice size. The show has a subreddit and an official Twitter account (inactive since 2019). Interactions mainly consist of fanarts and manga readers. The community is active, albeit not really loud. No one seems to really wonder about season 2, which is understandable considering the original medium is still ongoing.
Will there be Trinity Seven Season 2?

The manga is written by Kenji Saito and illustrated by Akinari Nao. It started on December 9, 2010 and is still ongoing. It has 25 volumes.Two spinoff manga were also released: Levi Ninden (November 2015 – December 2016) and Liese Chronicle (February 2017 – June 2018). By July 2017, it was announced that the manga had more than 3 million copies in circulation in Japan. The main manga has been licensed in English by YenPress. The light novel is written by Saito himself and still illustrated by Nao. Publication started on November 8, 2014 and it is ongoing. The 3 volumes focus on certain characters’ past and events not seen in the manga.
Trinity Seven received an OVA (considered to be the 13th episode) on March 25, 2015: the episode is anecdotal and offers some fluff and fun. The license was also adapted into two movies: The Eternal Library and The Alchemist Girl (February 2017) and Heavens Library & Crimson Lord (March 2019). The first movie directly adapts the second volume of the novel series and the second movie adapts the Magic King Abyss Trinity arc from the manga. Sentai Filmworks released the complete season on Blu-ray in August 2016. A mobile game titled Trinity Seven: Phantasm Library & Seventh Sol was released in 2019.
A lot of goodies surrounding the title are available and diversified in shape (plastic stands, OST, posters, straps, badges, etc). Certainly due to the fact that the manga is still published and having some success, a lot of those are still available. When checking Google Trends, we can see that the graph never actually reaches 0, even if it gets close to it once. Otherwise, the search queries are stable and show some activity. The map is even more telling with a lot of countries painted in blue.
When will Trinity Seven Season 2 be released?

No date is available as of yet.
What can we expect in Season 2 of Trinity Seven?

Trinity Seven is a weird bird: it is not a big title à la Attack on Titan, but it is clear that it is successful and has an audience. It is difficult to understand why a second season has never seen the light of day. The studio even got better animation-wise: their last piece, Blue Period, is visually pleasant.
Some speculate that it might be because the future arcs require higher techniques in animation, something Seven Arcs cannot cover yet. All in all, if a second season ends up on the table, there is enough material out there to even give it two courses. It would allow the fans to finally see some real action and Arata’s training as a Demon King.