In the next Megaten (more than likely the next Persona game because it's the only one that's been announced) I'm not sure what I would like to see. They kind of almost have all the theatrical things I'm interested in, and I love turn-based battles to death.
The social link system is fantastic. I would like them to keep it but upgrade it a little. I'm not sure how. Atlus are way ahead of me in terms of progressive thinking in JRPGS (and way ahead of alot of their competitors). Take it in any direction they want, as long as they keep the same standard of excellence. Maybe a Persona game in the 70's or 80's. I don't know why, it just seems like that time is mostly left alone in terms of story.
Of course you can't go too far back in time in Persona games because the whole point is that it's believable teenagers in a High School environment.
This is a very difficult question, it's a bit like if my favourite author came up to me and asked me what their next book should be about. I am merely a consumer, feed me and I shall consume.