Just like you said you can only do one Wii U + one 3DS locally. Same with 4x Wii U's on wifi but nothing more. They said they were gonna allow a patch to use your Wii U as a kinda wifi connectivity thing for a 3Ds to play online with the 3DS but you cant use the Wii U while it's in that mode. They are kinda heading in the direction of the PS3's Ad-Hoc party where you can use your PS3 to connect a PSP online and play onilne like that. Though they said taht the next monster hunter 4 will have online play for the 3DS not just local.