Katsuhiro Harada, producer at Namco Bandai and project leader for Tekken Tag Tournament 2, said that the new game needs some "creative ways" to cope with a processor that may not be up to par with the competition. Harada told Digital Spy that the Wii U processor clock speed is "kinda low" and that this circumstance requires some extra effort to make the game work as expected. He noted that the clock speed may be "a little bit" lower than that of the Xbox 360 or PS3.
The clock speed itself is not so much of an issue, but the statement that software game development needs "creative" solution to deliver the HD claim of Nintendo is not flattering. However, he did not provide any more information what the true problem is - and there may not be a problem in the end if developers find a way to work with the Wii U CPU. On the bright side, the GPU was said to be "not much of an issue."
Nintendo is already facing quite a bit of headwind and doubt that it can deliver a game console that can upgrade the Wii and offer a compelling alternative to Microsoft's Kinect. We would hope that Harada's notes are rather a hiccup than a serious concern that will hold the Wii U back.