Here's a bit of a conversation between two people that supposedly have inside knowledge of Wii U dev kits. They're discussing the talk of earlier today pertaining to Wii U dev kits going wireless in June.
Person 1: Really weird, it's conflicting with what i've heard. I'm pretty sure the dev kits, maybe at least from revision 3 (and more surely for revision 4), have the option to switch between wired and wireless mode. Now, maybe the DRC weren't wireless until a few months, but even then, it should be the case now. I could be wrong though, perhaps the dev kits themselves are ready for wireless communication with the DRC, but the DRC prototypes in possession of third-parties aren't.
Person 2: Yeah, seems strange. Maybe their sources are smaller/ less important studios and really won't get the newer pads for a while. The latest pad (product id DK-DEV-V5) is wireless. Also looks like Nintendo uses Ni-Fi for the controller now (2.4 or 5GHz), so range shouldn't be limited to a single room - possibly not even just a single floor.
“Nintendo… has to release hardware that’s of the expectations of the gamer today. “… I don’t think we would be bringing the game to a system that would be inferior to current gen. (HD) systems.” - Craig Harris, SEGA (Ex-IGN Nintendo)