As most of you know Persona 2 was split into two separate games. Innocent Sin, then Eternal Punishment.(I'll get to how that relates to Persona 3 in a minute).
Minato's essence is still alive, just sealed away in Nyx, so he's not technically dead. In Persona 4 Margret mentions to Yu Elizabeth left to find a way to free "the blue haired boy" from his seal. Along side that there are constant references in Persona 4 Arena about him. We also learn into some more about Mitsuru, Aigis, Akihiko, and Fuuka(a bit) on where there lives took them after the events of Persona 3.
Now you might have noticed they did leave a lot of cliff hangers for the Persona 3 saga. Such as what happened with the characters between the events of P3 and P4A. How much has Elisabeth actually accomplished within her time away in trying to free him? And most of all will we see his return anytime soon?
A lot of Persona 3 fans hope he will come back in Persona 5. That is more then unlikely to happen. This brings me back to Persona 2 being split into two games. In the first you play as Tatsuya, while in the second you play as Maya. In both Persona 2s both characters played major roles, just when the later game came the protagonist switched. I think its more likely we will see something like that again with Persona 3 rather then seeing him in Persona 5. As in a second Persona 3(part 2). Maybe Elisabeth will become the next protagonist or we'll have Aigis again like in "The Answer". Minato most likely won't be the protagonist of the story when he is freed(just as Tatsuya wasn't in the second part/game of Persona 2).
In the case that they do bring him back in Persona 5(which is unlikely), Elizabeth and/or Aigis would most likely join the new partys team in one point of the game, bending the story to relate to Persona 3 and Minato...saving him and completely destroying Nxy. We saw something like this in Persona 2 Innocent Sin. Yukino(from Persona 1) joined your party, and we saw some appearances from other Persona 1 characters. You might think why not do this? Well its simple. Atlus most likely wants to attract more fans to the series. Making a direct sequel off of Persona 3, when Persona 4 barely comes off the main story of 3 could be a little irritating for newer fans(as in just 5 players(and maybe some 4)) or people who haven't played Persona 3. This would be a bad business move for them since the player would have a hard time getting into the plot of the story and trying to figure out who half the characters are. The difference between them doing so in Persona 2 with Yukino is because it didn't effect it into the main canon of the story to much. Though there were tons of references to Persona 1 while they kept the story for 2. Also take note how close the original releases were for the original Persona games(1, 2IS, and 2EP). We have a much bigger gap of the releases between 3 and 5.
In the end of Persona 4 Arena, its hinted that Yu and the gang are going to head to the city Persona 3 took place in. I highly doubt they would bend saving Minato into the next Persona 4? Arena game. As said before Atlus wants to keep new people getting into there games(= more sales). In Persona 4 Arena they re-explained the plot of Persona 4 Arena in a good amount of depth so newer fans wouldn't be confused. Also take note some fans of just Persona 4 were a bit confused when Aigis and the other appeared(not knowing a lot about Persona 3. I'm not pointing anyone out but I've been seeing confused P4 fans on various sites.) A lot of fans were confused about this since they didn't go to in depth in Persona 3s plot. And remember Persona 4 Arena is a spin off(in a way) of the series, its unlikely they would make the story canon to the rest of the series.
Atlus obviously hasn't let go of Persona 3 yet, especially since they are making the movie as of now. You can bet Persona 3 fandom should go up after that just like Persona 4 the Animation made its fandom go up. Its likely we'll see some more things to do with Persona 3 once this movie is released(maybe a trailer at the end of it for a continuation game lol).
Thanks if you read all of this and understood it. I've seen this discussed a few times but it never went into to much depth. So I made this topic...