Its pure speculation at this point. We haven't even seen gameplay footage, let alone marketing or publicity from Nintendo itself.
My take is that, if Sakaguchi couldn't help sell XBOX360 and DS units in Japan, then he may not be as strong of a force as people believe he is. His Wii offering may be just that, his 'Last Story' to prove if he can deliver a game to satisfy the masses beyond just Final Fantasy (or a game similar to it).
As for Xenoblade, its a sequel of a sequel series of a game that was on Playstation. There's really no way to gauge how well it'll be received. Frankly, I feel its gonna be an uphill battle to make that title popular and even after all that work, it may only sell to those who already liked Xenosaga at the end of the PS2. Which wasn't much (Xenosaga Episode III only sold around 180,000 units total). So while the 'name' of Xenoblade is big, its sales may not be. The only way they may get people to buy the game is a big media push and trying to market it as a totally different game.
Six upcoming games you should look into:
