Oh God, my wallet is just crying, thinking about it.
Obviously, a new PA Kai line will be announced. I mean, they released the new AC Kai's because the old ones were so....bad. They were the second or third PA line at the time, the oldest and worst being X-2. But anyway, Square is definitely not shy to milking VII merchandise. So I anticipate a complete Kai line... a second Cloud, possibly with the Daytona like last time, maybe even a Cait Sith with Moogle.... we have Red XIII who doesn't change at all, but we'll likely see another Tifa, Vincent and Yuffie, and new additions like Aerith and Sephiroth. Whether they'll redo Barret is anyone's guess, since it took ages to get him the first Kai anyway. And Cid is announced but has yet to be seen.
I would die for a Midgar model. Just, urgh.... can't comprehend the awesosomeness of how that could go.
A weapon's Kai line would be good, bring that back again with either Ultimate Weapons again or noteable weapons. (Not sure why Cloud's Hardedge is always made?)
Possibly another statue line... They've had the Kotobukiya's, based off Nomura's artwork, the Cold Cast statues which take memorable moments of the series, the Sculpture Arts which does the same but more upscale and sophisticated, and then the Static Arts, which are bigger, brighter and more vibrant, but made out of hard plastic, so more durable. I could see SE doing a new line again, because, really, it's VII.
And, probably, another chibi line. The PA Kai Mini and Static Arts mini are all well and good but, like, come on.
What I would LOVE to see, is a homage to the original game. Do hard plastic models of the original game characters where they're blocky and lego like. This was seen once and only once, when someone took the ingame models to a 3D printer site and started selling them at cost.... which lasted about 2 weeks before he got the kaibash. I get it, legality and all, but seriously, LOOK HOW AWESOME.