I can't imagine a world without Nintendo making a console. Even moreso I can't see them making software for their competitors. They would jizz their pants over their exclusives. It would be amusing watching the bidding wars for Mario though.
The fan base is much too large, imo. Although, I bought a 3DS and it's bollox.
Same here, Nintendo is a true giant and their exclusives alone make them an integral and invaluable part of gaming. But that doesn't mean they can rely solely on their exclusives (or waste them like they do with Metroid) and neglect the rest. In this casual-friendly, connected BS of a world we live in they absolutely need to consider two things:
1/ Enter the mobile sphere with their next handheld, one that could play exclusive games for their 30-something fanbase but with a form factor that both allows for physical controls and touch capabilities tailored (or dumbed down, depending on where you stand) to the casual crowd, doubling as a kid-friendly - and affordable - smartphone for the younger folks who doesn't want or need some fancy £400 iStuff.
2/ Clean up their online mess on the console side, with a Nintendo Network that's a real, serious rival to the xbox Live and PS+. Bluray player, HDD and a real digital store straight out of the box. Oh, and Metroid Dread also.