Sumo Digital’s was asked about whether or not the Wii U version of Sonic & All-Stars Racing Transformed would support online voice chat. Here is what Sumo Digital said:
We don’t support voice chat on WiiU for those reasons, one of the side effects of being a launch title basically.
Yep, Sonic & All-Stars Racing Transformed will not be a game that will support in-game voice chat on the Nintendo Wii U.