I'm in close quarters with several GameStop managers. They are ALL jonesing for the Wii, consider the PS3 nearly insignificant and cite that Wii has generated some of the most demand they've seen. Remember, these guys have been to the recent shows - they've played all the platforms (and not for 30 seconds at a Nintendo Fusion Tour). What does that say? I dunno - but my money is on Wii.
Don't you worry A THING about RPGs on the Wii. Square-Enix is so far in the closet with Nintendo (some of the Top 10 Nintendo DS titles are the breathtaking games from Square-Enix). I have NO doubts that they are hard at work on Wii titles.
That being said, if you don't have a DS yet and are into RPGs, you might want to consider picking one up. FFIII is unreal.