Wouldn't that be nice? 360 with motion remotes.
I think the only way the Wii can gain & hold it's ground is if it manages to keep that awe-factor. This can be accomplished through new hardware innovation or software innovation (i.e. new controllers, or new games, respectively)
Even if the Wii's long-term evolution is somewhat linear and uninteresting (which would be odd, considering Nintendo), it will most likely still make a great general entertainment piece for parties or social gatherings.
Keep in mind though, I do not own a PS3, 360, or Wii, despite having used all three of them, albeit casually.