Zelda and a 3D Mario could realistically both be ready for that launch window.
The 3D World team has largely been free since fall 2012, by 2016 you're getting into *four* years without a new project from the main EAD Tokyo team.
Zelda can be Twilight Princessed.
Bada bing, bada boom. There's your launch window.
Even Mario Kart 9 for NX is likely well into development by now, the dev team there wrapped on MK8 a year ago.
What kills Nintendo is they have to support 2 platforms, so when they were launching the Wii U, they exhausted themselves trying to save the 3DS and focused a ton on the 3DS, which then predictably led to a large lull in Wii U software. Now they are releasing more Wii U games, but you can see 3DS owners are upset because they're not getting a good flow of games.
If you unify, this isn't an issue, Nintendo would be able to focus on launching one product and could easily release several good games within the first 6-8 months. So launching in 2016 wouldn't be an issue if that's the direction they're going in.
