Coming from Yuri L. Araujo, Associate Online/Community Specialist, Capcom U.S.A....
As for the online support, we've announced the Wii U can go online. 3DS has local multiplayer only. If that's something you really want to see happen, head on to the MH forums and start talking about it there - then I can bring it up the chain with some supporting evidence. =)
It's certainly going to be a unique choice for the fans here. Which one do you buy? Do you pick up both?! Thanks to Alex for the heads up!