It appears that the Wii U won’t have voice chat as an out-of-the-box feature.
Understandably this is rather peculiar seeing as the GamePad contains a built in microphone and Nintendo even released a trailer showcasing some potential voice chat functions. However, according to Kotaku, this won’t be the default option for voice chat.
Instead you can pick up licensed headsets to plug into the GamePad and use if you want to. Interestingly manufacturers aren’t offering any wireless versions as of yet, which suggests that maybe the Wii U doesn’t have that capability either.
MCV also pointed out that Call of Duty: Black Ops II supports voice chat and the Wii U Pro Controller, which strangely has no port for a microphone to plug in. This means that anyone wanting to chat whilst killing each other needs a GamePad nearby to plug some headphones into.
It’s all rather cumbersome.