[quote name='lilboo']I doubt any 3rd party games would make games revolve around the Miis. I think that's something Nintendo is only going to do. I don't even see alot of "Mii Games" coming out at all. It's Wii Sports and Wii Play right now. What else would they do? Use them in AC? That would be cool, but would look different..but whatever.
Maybe even a "Wii Sports 2" (it HAS to happen.)[/quote]
I'm sure there'll be a Wii Sports 2, or even a full-fledged game for each of the sports in Wii Sports. It'll happen.
As for 3rd parties using Miis, I'm sure more companies will use it (and turns out, its already happening, thanks to The Sims).
Sooner or later, a company is going to realize that they don't have to make characters that look like the ones in Wii Sports to take advantage of the Mii system. Simply read the facial structure of the Mii in the system, and apply a similar, more realistic (or cartoony, or whatever) look that matches the Mii's facial structure. Simple. Now you have a Mii system that can be easily applied to games like Red Steel 2 or Tony Hawk.
In regards to expanding the customization of Miis, I can totally see it happening, but what will become of games that are programmed for the old Mii system? Unless Nintendo has already properly programmed and planned for Mii expansion in their games, or better yet, in the Mii application itself, then older games might be locked into the current system. So if Nintendo updates the Mii system, old games (like Wii Sports) might go crazy trying to figure out what this new facial feature is, or why there are accessories or color combinations.
Hopefully Nintendo has planned for customization expansion, and that won't be a worry.
Edit: Darnit! Sir_Fragalot beat me to it.