Soundwave on 12 April 2016
I doubt they would be doing ports to Mario Maker and Splatoon (or even considering them) if there was basic backwards comp.
Backwards compatibility isn't going to take Nintendo anywhere, if this is a "traditional" console then they'd be better served just shutting up about hardware and giving third parties whatever works best for them and that tends to be x86.
You cannot make third party ports any harder than they have to be because they likely aren't to sell that great on a Nintendo platform, not for a while, so the investment needed on them needs to be as low as possible (time/resources/money wise).
The moment the porting is too hard, guess which third party port is first in line to get canned? Hello, Nintendo.
