Just watched the trailer over on the Squeenix website, and I am so looking foward to this now! Obviously, Tifa, Lightning and Kain are confirmed, and all the old characters are back.
I was having a good long think about who else I would like to be in it be in it, and I have come up with this. I am thinking they pick one more from each.
FFI: Black Mage (just call him 'Black Mage')
FFII: Minwu
FFIII: Refia, but do what they did with Luneth and name her after a job (not sure what though)
FFIV: Kain (already confirmed)
FFV: Galuf
FFVI: Locke
FFVII: Tifa (already confirmed)
FFVIII: Seifer
FFIX: Freya (please, please make this happen)
FFX: Seymour
FFXI: (don't know, don't play it)
FXII: Basch
FXIII: Lightning (already confirmed)