To the Wii: no. Not unless sales of the other consoles utterly stagnate, as in PS3/360 don't sell another unit after this Christmas and Wii is the only option. FF is Square's flagship series. It's always (or at least since VII) been about setting new standards in technical achievements, and I don't see that changing anytime soon.
But as for the next generation, I don't see why not. People talk about Square's "loyalty" to Sony, but what they fail to realize is that for the last two generations, FF games simply haven't been viable on any platform other than Sony's. In the PSX era, the N64 didn't have the storage format needed to handle FFVII-IX. In the last era, the PS2 was so ridiculously dominant that it wasn't worth the bother. Only now, with the 360, is there finally a viable competing system. The Wii isn't, but if Nintendo's next system is technically on par with the competition (and maybe it won't be, given Nintendo's current strategy), there's no reason it shouldn't be a possibility for FFXVI onward.
For the more immediate future, this is how I see it playing out: FFXIII will remain exclusive to the PS3, unless it's a complete sales disaster. In that case, we'll see a 360 port a year or so down the line. FFXIV is very likely already in development, and I've got a hunch it'll be an MMORPG. In that case, it'll be released on PC, PS3, and 360 all within a short period, maybe within a year or a year-and-a-half of XIII. If it is an online game, it's in parallel development by the online team, which means FFXV is probably also already in pre-production. The platform status of that one will be determined by market conditions closer to its release, but if things continue anything like they are now it'll very likely be on both PS3 and 360. If PS3 gets its act together and/or Sony offers a very sweet exclusivity deal, it might remain PS3 exclusive.
There's my prediction: the next 3 games will all make it out this generation, but not on Wii. After that, anything's fair game.