I would not be surprised if the WiiU was the last Nintendo home console, but I would also not be surprised for them to go on to dominate the handheld market for some time. I would be very surprised if the company as a whole collapsed.

I also do not think it is selfish to want Nintendo to go third party, because Nintendo will still make money from the games they make - indeed, they would make a lot more because the sales would be vastly higher with a greater market to access. Simple economics! I also do not think it is selfish to want a whole new generation of fans who have no interest in buying the WiiU (because consoles aren't exactly cheap) can enjoy them. I think the Mario, Zelda, Metroid etc. franchises would get a massive boost if they were on the Sony and Microsoft consoles.