Soundwave on 20 August 2015
NX is primarily the successor to the 3DS, it will just happen to be able to also function as a console because mobile chips have gotten massively more powerful over the last 3-4 years, it will be more powerful than the Wii U as a result.
So if there's backwards compatibility IMO it will be with the 3DS/DS.
I think Nintendo is done with disc media after this gen too.
You will be able to play some Wii U games on NX ... in the form of remasters/ports (DKC:TF, Pikmin 3, Xenoblade and probably a handful of other games I can see being ported). And you'll have to pay again for those games.
Which is the smarter business strategy anyway.
