Saelune said:
Why would a device made to be able to play Wii U games allow you to play 3DS games?
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.
Dreiko said:
NX is confirmed to use cartridges and if you have a 3DS already upgrading isn't that big a deal. If you never had a 3ds then sure but I'd just get more games. Unless you really wanna play a portable inferior xeboblade port.
Rumored*
OT: If you already have a 3DS, then wait till you see what the NX actually is. Unless there's something specific to the New 3DS that you really want. In which case you choose the regular size if you want custom faceplates, and the XL if you want a bigger screen.