If you are planning on picking up Sonic & All-Stars Racing Transformed on the Wii U, I might have some bad news. It seems that the Wii U version will not support voice chat. As you know, Wii U will be online chat capable, but will be done on a game-by-game basis and require you to get a third-party headset instead of using the Wii U GamePad microphone.
“We don’t support voice chat on Wii U for those reasons. One of the side effects of being a launch title basically. Does support it on PS3 and 360 though!” - executive producer Steve Lycett
Seems the problem was time, since the game is a launch title it’s hard to get all the features you want into the game. Other launch games that do support online chat include Call of Duty: Black Ops 2 and Mass Effect 3: Wii U Edition.