IDK, Sony is ran like a business and the PS1, 2, 3 and 4 have all had great libraries.
If they end up having to go third party, so be it. I don't buy the arguments that they'd diminish like Sega. Sega had far bigger issues like screwing over fans with the 32x, Sega CD and 32x, having too many of their games being arcade type games that largely died off as people moved onto narrative driven games and competitive online games vs. replaying short games to try for high scores etc.
Nintendo's biggest games like Smash, Mario Kart, mainline Mario and Zelda games, Metroid etc. would do fine on other platforms. Things like Pikmin would do fine as $40 releases ala the new Ratchet & Clank. Smaller titles like Captain Toad would do fine as $15-20 download only titles and so on.
Plus with the business folks pushing them to expand mobile, expand licensing of their IP etc. just brings in more revenue that can be used to fund more games.
Nintendo isn't going to willingly just go third party. Shit will have to be rather fucked for that to happen...just like Sega. The Nintendo that survives that change will not be the Nintendo everyone just assumes it will be. This pie in the sky idea that 3rd Party Nintendo would now be free to release all the games people want is unrealistic and naive at best. For Nintendo to go third party, that means their war chest is gone , perhaps super far into the red. That will mean they also have begun to leak their talent elsewhere. Third Party Nintendo is more of a Mario/Zelda (and perhaps AC) factory than it is now. Those are guaranteed sellers and thats what they bank on. Look at every other 3rd party, they rely on known properties to stay afloat. Capcom has none; they are dying. Ubisoft has AC; Doing pretty good. Sega has fuck all; might as well be dead (;_

NOW I will say, I don't think Nintendo would flop and die (even if being at the edge is probably the only reason for going 3rd party IMO) but I don't think it is the sunshine and roses people are making it out to be. Being a third party isn't exactly poppin for people right now. Many former titans are leaking right now and are having a tough time keeping up...especially the Japanese Ones