I like the one year premise as NeoCracker said, the games are pretty damn long to begin with and I feel the pacing of the 1 years (really its more like 9 months for both entries) is pretty much perfect as it is long enough to get a lot done in both the story and gameplay, but short enough to make 100% completion very challenging on a first play-through. I mean the games thrive on New Game +.

As for Minato and the ending to the Answer, I'm with NC, I felt the Answer presented a pretty good conclusion to the P3 cast. Minato (P3 MC) found his answer and made his choice, and I feel the heroic sacrifice he made is fitting. Erebus is pretty much a standard Lovecraftian monster so I can't really see it going down without someone either wiping out mankind or forcing all of it to reach some perfect hive mind status. Considering Elizabeth is trying to stop it for good, I can see her contemplating either as a viable option.

With that said, I don't think it's implausible that he may return in future installments. He's a very popular character with the fanbase and P4, and especially P4 Arena tease the player with the prospect of finding a way to free him, so I think it's very plausible Atlus would cater to the fanbase and find a way to set him free, but I kind of hope he keeps his ending. I am actually hoping that he would be a future DLC superboss for P4Arena, Elizabeth's comments about him in some of her victory quotes makes him sound frightening powerful.

I actually want fusion spells to return, I was pretty peeved that P4 and P3P dropped them for a far more tedious alternative. Though if they bring it back, do it like Persona 2 and have the fusion spells with other party members. If they are doing the party member social link thing still, just have it another convenient upgrade bonus.

I also hope they keep referencing the older games and having walk-on of older characters, though I would to see it expanded to earlier entries like have the party go to an indie band concert and see Ekichi's band from P2. Little things like that would be cool.

I also kind of hope that P3P gave them some ideas on how to utilize and expand the gender option cause I think it would be cool to play-through the game as a guy and then on NG+ play-through as a girl.

Also, remove the dizzy status effect and just return the Press Turn System back to P3 rules cause melee seriously loses its edge thanks to having to critical hit or exploit an elemental weakness twice on an enemy or character to lose a turn.Especially now that the game has implemented the ability for party members to help each other up when knocked down.

Keep the weather skill forecast system, it was neat and keep P4's version of the Shuffle Draw, it's way more interesting than P3s.