Sakurai's hand isn't much of an issue, he has Bandai Namco on his side. I've seen the pic of him using 2 controllers so I know he playtests too but a whole dev team can fill in the blanks. Plus they can reuse several assets from Brawl. It took a while to create a huge amount of characters from Brawl to Melee so it took longer then.There isn't even a release window more specific than 2014 yet. Brawl had its original release date announced six months ahead of time, and Nintendo still seems to be doing this sort of thing.
Plus, Sakurai's hand is in such a bad condition that he's thinking of pushing the launch closer or further away than it currently is, and knowing Sakurai, he'll take as much time as he thinks he needs.
And it's been in development longer than Brawl? Remember that we're talking about two games on two platforms. They have to work out balancing, online infrastructure, exclusive features and stages, and stability for both games.
As for the 2 platforms, one can release before the other. We have seen a lot of the game already, it looks pretty far along. We can argue that since there haev been less characters revealed we aren't close to release until at least past October, but I'd say he'd vastly increase reveals closer to a possible late August or early-mid September release. If we don't get an idea of when it releases in the April direct like which quarter, then I'd say late September to mid November.