Except developers already have ports/versions of games announced, and they wouldn't do that if it was underpowered. And people like the Darksiders developers, who actually have the balls to go on record with their name, basically said they had no problem getting their game up and running.
Is there really anyone stupid enough to hold on to that this system won't be able to run what's coming out for 360 or PS3?
This is why stupid rumors get such legs, as long as there's someone stupid enough to believe them, they're stupid enough to post it to get hits.
A port doesn't have to be as good or better, it can be worse. Just because thy have ports of announced titles doesn't mean the WiiU is more powerful than the current generation consoles.