Zel: Probably working as a bodyguard for a certain princess in Seyruun. Amelia will probably be crown princess by then - Phil's not likely to be dead, but the actual king might finally have kicked the bucket.
I mean, unless Naga shows back up, but that's possibly even less likely than Prince Phil biting it.
Jak: probably still hanging around racing and maybe Wastelander-ing (unless the end of TLF did something weird, I really need to at least watch the cutscenes one of these years). Maybe married to Keira.
Maybe also with kid(s). Because the image of Jak giving his kid a piggyback ride and being steered by the ears is too cute :3
Leila: Going just by canon? DEAD (imagine this in the scrawly Homestuck "DEAD" thing). Leila will have been familiarized with stabbity death before FE7's even over, if I ever get there.
I haven't decided yet if someone on the community having saved her (should that happen) would result in her staying on Elibe or getting shuffled off to another world. She'd like to stay in Elibe, I'm sure.
In which case she'll probably be married to Matthew and they'll both be retired. Probably kids will happen (and if that was actually possible they might end up joining Roy's crew).
Butterfly: Well, in technical terms she'll probably be the Emperor's daughter by then.
On the assumption that Last Hero takes place less than ten years after Interesting Times, and when Cohen leaves to go meet the gods Twoflower succeeds him, being Grand Vizier and all.
She may possibly be attempting to bring big sweeping reforms. How successful they'll be is anyone's guess.
Maugris: may still actually be in Hinoto-Ri in ten years' time.
If he actually goes back to his world he'll probably find things very different (due to how the game he was in ended), and will probably light out for California and defect to the Anarchs, Tremere be damend.
Assuming he doesn't get sidetracked sticking his nose into other people's business in the name of helping.
Erk: Probably will have retired somewhere quiet in the Etrurian countryside to study magic. I haven't been playing him like any of his paired endings are canon, so no sudden babies for him.
It'll be five years after that before Sword of Seals kicks in, and who knows what'll happen to the former Mage-General's apprentice then.
Special bonus: Ssilissa: Will be queen of the m-fing Snilth and living on Hades (what we call Neptune). Snilth get ideas into their heads so fast that who knows what their society will be like by then.
Rose: Will be dead from wall in canon. If I ever get around to apping her into Strings she'll probably end up staying in Hinoto-Ri; she'll be middle-aged by then, what with the whole aging in seasons thing.
Or she'll go home and marry Martin and seriously derail canon because they'll probably end up staying in Noonvale and Redwall will never get founded :x