Nope not at all.. Even if they recieve a major blow with the 3DS and Wii decline like you say, they've earned a ton of profit from Wii and DS to the point where they could probably withstand a major decline and still be ok. If they can survive the Virtual Boy, Gamecube, N64, etc, they will no doubt be fine now.
I don't know where some people are getting this doomsday stuff about 3DS. Sure, it probably won't sell as well as the DS, but then again what will? It still seems to have a really strong library, particularly of third party games, where Nintendo consoles are usually lacking, so by that merit alone it should recieve decent sales. As long as Nintendo provides a strong library, it will sell, simple as that. And if and when Nintendo ever wisens up and throws out anothe 2D Mario for 3DS, forget about it.. the thing' sales will become monumental.
