No they should just design their next consoles to share a part of their game library.
Right now they waste a lot of their resorces to develop the same IPs twice to reach both home consoles and handleds (Mario 2D, Mario 3D, Mario Kart, Mario Party, Zelda, Animal Crossing, Yoshi, Kirby, Smash Bros) while they could just make a single multiplatform entry. They could even design these games to have slightly different features and multiplayer modes depending on which console you play.

I'll add many 3DS games like Luigi's Mansion, Link Between Worlds, Fire Emblem Awakening, etc. could fit perfectly an home console, just like WiiU games such as Tropical Freeze or Captain Toad could work perfectly on an handled.

No,even with a small install base they can still sell a shit ton of software (is it 6 or 7 million plus sellers so far?) Even Wii U will be a profitable venture for them in the long run.

Most likely the console will have a standard 5-6 years life cycle... but they could extend it a few years with the unified platform everyone jumped ship on and made a hybrid system. Just make the next 4DS platform similar to WiiU's hardware with a 720p screen (easier said than done) and titles would be compatible between them by default. Provide an SKU with the WiiU console and the 4DS as a Gamepad substitute and you got your hybrid there.

... but I already said last year that this sounds just like a PS4+Vita, so scratch all that xD

I agree completely, in previous generations it made sense to have seperate handheld and home consoles due to the huge gap in power/visuals. We are starting to see it now with 3DS/Wii U that the difference in hardware & software is not hugely different outside of a few cases. Both are fully capable of producing 3D worlds, both have gyroscopic motion controls, both have dual screen/touch controls and games like Mario 3D Land/World, DKC Returns 3D/Tropical Freeze, NSMB2/U, Mario Kart 7/8, Smash Bros 3D/U arent vastly different.

Its time to unify the handheld and home consoles by giving them the same architecture and similar specs that can play the same games. The next handheld being somewhere in between Vita & Wii U in power and the home console being somewhere in between Wii U & PS4 in power. Something like the handheld being at 720p and the home console at 1080p. Not only will this ensure that Nintendo no longer has huge gaps in releases, it also opens them up to create more new ip and resurrect older ip since they wont need to make 2 seperate games for all there franchises. Also this will ensure that Nintendo's home console will have all the Japanese 3rd party support that the handhelds enjoy.