The 3DS one is coming soon-ish. At first I wondered why, as the Wii U is struggling sales-wise but they certainly have no problem selling 3DSes, so you'd think they'd want more console-selling "killer app" software out of the gate for the Wii U. But when I think about it, the Wii U will probably do better with Mario Kart 8's release at the end of May, which everyone will be playing for a while, so best to release Super Smash Bros. For Wii U in the winter to keep the momentum going then.
Plus presumably the Wii U one will take more to develop, and it will feel more like an "upgrade" rather than if they released them the other way around. I don't look down upon handhelds but I'm sure many people see it that way. They'll probably sell quite a few 3DS copies though, considering that within each household, each player is going to need their own copy!
But, as exciting as the 3DS's relatively soon release is, I'm behind on my 3DS games! I haven't even picked up Bravely Default or Professor Layton And The Azran Legacy! For that matter, I've been meaning to find Mario & Luigi: Dream Team and Paper Mario Sticker Star! And I'm still working on Pokémon Y! (And four of the five games I just mentioned are RPGs, so that'll take a while...) Too many games to play! Yeah, I know...first world "problems"... Though I wish the Wii U had the "problem" of too much to play...
My brother's more of the Smash Bros. fan, but there's no way I can't be excited too. Let's hope it doesn't get delayed into 2015...though I might forgive them if they decide to add a story mode after all.