Like I've said before, the Wii U version will take at least 3 years to make because it'll take a huge amount of time to make a HD fighting game with over 50 characters. Hell, right now the only HD fighting game that has anywhere close to that many characters is Ultimate Marvel vs Capcom 3 which has exactly 50 characters. That game was just an expansion of Marvel vs Capcom 3 which first started development back in Summer 2008. So yeah, it's going to take a while.
The only bright side is the 3DS version will probably be done in less than 2 years. Since the 3DS game will probably just use Brawls engine and reuse a lot of it's existing assets, that will save a lot of time. In particular, all the returning characters from Brawl will only need minor changes for the 3DS game since the 3DS and Wii hardware are very close, while the Wii U version they'll all need to be made from scratch because the Wii U is lightyears ahead of the Wii. This is why the 3DS will be more than likely be done much sooner which should help with the wait for the Wii U version.
I still predict that Smash Bros 3DS will be a late 2013/early 2014 release, while the Wii U will be mid 2015/late 2015.