Kibeth41 said:
If it could, then why would it not? The Gamecube let you play GBA games. And the Wii U plays everything except 3DS games via virtual console.
Chances are it won't. Just because the console uses cartridges does not mean that it'll use the same cartridges as the 3DS. It'll probably play 3DS ports. But there's nothing to suggest that it'll be backwards compatible with ANY console other than speculation.
Gamecube required a Gameboy adaptor, and the Wii U doesn't let you pop in your Gameboy games.
Not saying it doesn't have the power to play them, but doesn't mean it will, even if it uses cartridges. The NX may use cartridges, but it doesn't guarantee it will play 3DS games, or DS games, or anything but whatever is made for the NX.