I don't have any games that support multiplayer voice chat, but I just heard that 4 pole headsets work with Wii U. I have a pair of Astro A40s with a 4 pole plug, but I don't have any games to test it out on. Boo! I hope they work when I get a chance to try them out. They just have to be plugged into the Wii gamepad.
If you don't know what a 4 pole plug looks like, they look like this:
The different 'stripes' carry stereo audio AND mic data. It's like the kind of plug on the iPod earbuds that have an in-line mic. I understand the iPod headphones work great with the Wii U for in-game chat. Anyway, if you guys have a multiplayer game and some iPod headphones with a mic, try it out and report back. And if anybody has a pair of Astro A40s, I sure would like to verify if they work or not.