I'm not sure this assertion is true in any sense (The XBOX360 even launched before the Wii, and I doubt it will win anyway at any time)
Ehh, I should say "in the hardcore console market". But anyway, 360 is doing quite well over Wii right now. ps3 and 360 combined (and theyre really the same console compared to the wii, differentiating them is somewhat arbitrary) ever more decisively as time passes. Which is where the "time" thing comes in...
More or less the PS360 (same, more powerful console) did in fact beat the Wii. Wii is dying incredibly fast because it lacks power, while the others are gaining strength the older they get. Though I'll argue Wii didnt play in the "hardcore" realm anyway. That's more a testament to the fact that apparently the hardcore market is bigger (certainly more dependable) than the casual one.
But look there is no arguing this, if a more powerful console comes along in time it will eclipse the others, and thats a fact like sun rising in the east. The ps2 came out because dreamcast forced it, same with the Snes because of the Genesis. It's a law. Look at every developer it seems now crying for a more powerful console to switch too (Epic, Ubisoft, etc.).
It's not clear to me yet that Wii2 will be "enough" more powerful to force PS3/360 successors though. If it's only a little bit, then they might be able to stick around if Sony and MS so desire anyway.