I'm thinking this newest Wii U update bodes well for the possibility of wired input.

[LiteTheIronMan]

we've all been freaking out about wireless interference, having all these Wii U Pro controllers in the same room and stuff. even if you want to use a GameCube controller it's still gonna be wireless.
well... the newest Wii U OS update allows for USB keyboards to be used.
what do you guys think? it shouldn't be hard for Nintendo to create/implement something that would allow for the Wii U to receive wired inputs through the Wii U Pro controller's USB cable, right?

 

[Chiroz]

The possibility of wired controllers is very real and I am willing to bet that it will probably become a reality very soon. But I don't think pre-existing Wii U controllers would be able to send wired commands as, even though I have no idea of the actual hardware and circuits inside the controller, I am fairly certain it doesn't have any way of sending inputs to a device through wired means.

 

[IsmaR]

While I certainly wouldn't put it above them, feels like it's just not in the cards for the time being.

Perhaps as we get closer to Smash's release, Nintendo will react to the overwhelming demand/outcry and try to make a quick buck.