I agree. I've had that hunch for a long while now. I remember rumors of them making a console that can hook up to PC monitors and allow for networking and online play. I don't know if that idea is still brewing, but it's possible that they ditched it and started working on bigger and better things. Motion controls and the Wii in general are just a beta for what's next to come.
I'm guessing that they'll release another console with motion controls but so much better than the Wii (or PS3/360 for that matter). At that point, 3rd parties will have to just comply with whatever Nintendo offers or does to they're software. If you want your work on a console of the caliber I imagine, then you'd probably have no choice in that matter.
I'm rambling now, but I think that Nintendo definitely has some top-secret plan cookin' up. ^_^