I think semi regular revisions make sense for the handheld, but not for the home console, and they should not split the library/userbase for a long time. If you buy a Nintendo games machine, it should be supported with Nintendo game releases for a decent amount of time. Requiring you to buy a new version of the same device to play new releases would not go down well.
Enhancements that make sense for the handheld: An XL model that increase the screen size and resolution. A 3D model that play the same games at the same resolution, but with stereoscopy, a 3D XL model that does both.
That would let them release a new model every ~18 months without splitting the userbase. Then they can do an NX handheld 2, with full BC and increased specs for new games. Then repeat a similar upgrade cycle.
Edit: I guess revisions for the home console like a slim/mini model, or increased storage space make sense, but assuming the initial release is similar size to the Wii/Wii U (perhaps smaller if they abandon the disc drive in favour of a cartridge slot), they'd probably have more success with colour variants, like they did with the Gamecube and the Wii.