Nintendo, as a company, isn't going anywhere anytime soon no matter how many times we call doom on the company. Hell if anything they might outlive all of us on this forum.
With that said, there's no denying the fact that the Wii U is a flop of a console and Nintendo (as of a couple days ago) finally realized this. However, the Wii U alone is not going to kill Nintendo as a whole like everyone running around saying "Oh the Wii U is gonna kill Nintendo like the Dreamcast killed Sega and then they're gonna go third party and make Nintendo games on the PlayStation and Xbox and we'll all magically get blowjob's from the stuck up bytch that blew us off in highschool!"
What some people fail to realize is that it was not the Dreamcast alone that killed Sega, hell the Dreamcast was doing fine sales wise before it was discontinued. What killed Sega was that they were retards with their money and released flop after flop back to back like the Game Gear, and the Nomad. Then released too many peripherals for the Genesis like the Sega CD that only had a couple good games for it (literally two games worth owning), that stupid lock on thing that was ONLY used for Sonic 3&Knuckles and the 32X that only had one good game for it and it was a shytty Knuckles spinoff. Then go on to release the Saturn unexpectedly 6 months AFTER the 32X and priced it $300 more than the PS1 and N64 expecting it will sell better than both of them but nope, the Saturn's flopped and games just suddenly stopped coming right around 1998. Then Sega thought it would be a good idea to make Shenmue, a game that would cost them $80 million dollars to make and long story short, it didn't make even a quarter of that money back. Sega was flat broke when they released the Dreamcast (to a point where Sega employees were funding it with their own money out of their own pockets) but then Sega employees started to leave the company, big publishers like EA and Activision ditched support for Sega the company and to top it off, the PS2 was coming to crush buildings (and crush they did). When the PS2, Xbox and Gamecube came out and the Dreamcast sales dropped like a rock (they were practically giving Dreamcast's away for free), they had no other choice but to bow out.
Unlike Sega, Nintendo still has a shyt ton of money in the bank, the Wii was a huge success, the DS sold about as much as the PS2 and they run the dedicated handheld market with the 3DS, which was initially a failure. They even just opened up new development studios for their teams to work on more games and are working on the successor to the 3DS as we speak. Now will they make a turnaround with the Wii U like they did with the 3DS? Doubt it at best it will do reach Gamecube status and be a first party machine like the Gamecube before it. Is the Wii U gonna kill Nintendo, even though they still have billions more dollars in the bank than Sony in the gaming department? Unless Japan get's bombed to kingdom come again, Nintendo as a company will not die because of a single console's failed expectations. But it do agree that Nintendo has to get with the times and at least attempt to try to revived partnerships with third parties and work on games that are not just Mario and Zelda.
Sorry for the wall of text (I know a lot of y'all will look at this and go "nikka I ain't got time for all this shyt."

) but these are my feelings about the whole "Nintendo is doomed and will go third party" discussions.