Let me briefly explain. Nintendo switch apparently will be able to support custom engines made by devs, so there wont be one engine for console like it was in the 3DS. What if nintendo could make a virtual console engine for wiiU and 3DS? They could just create a new 3DS and wiiU emulator/engine or port the old one. Of course it would have to be downloadable content because cartridges are different from the 3ds ones on switch, and theres no place for CD. Also nintendo loves releasing accessories and variants to their consoles, sooo…. They could make as well an accessory that would support old cartridges and dvd discs!
I know that all the rumors said backwards compatibility won't be a thing, but hey, those are RUMORS.
Discussion started at here by mcdoge8