Color me skeptical. Now does not strike me as a good time to be introducing a new console. It’s doubtful Nintendo is going to get the huge mainstream audience it attracted to buy Wii Too, so introducing a new console would be abandoning the userbase they’ve developed. And if they’re worried about being underpowered … Moving first has some serious risks; the 720 and the PS4 can come out a year or a year and a half later, which would let them have better specs.
To me, it makes the most sense for Nintendo to drop the price of the Wii, and wait to announce the next Wii until after Sony or MS make the first move. EDIT: It’s going to be soon. I’d expect the successor systems to be announced by the end of 2012 (just in time for the end of the world and actually release around late 2013/early 2014.