Even if the Switch flops if Nintendo continues to make smaller portable devices mainly for the japanese market they can still create significant revenue for Nvidia.
Switch is high risk and to be honest so is Nvidia. They have screwed over Microsoft and Sony in the past. They are a very aggressive company who always seeks maximum royalties on their hardware. The original xbox may have continued longer if it wasn't for the fact Nvidia would not reduce their required royalties on the gpu.
Anyway consumers will dictate how long this relationship lasts more than Nintendo or Nvidia obviously.
What if Sony announces a x86 handheld based on xen architecture which will run base level ps4 ports at a slightly lower resolution on the go in March for release in September. I think that would absolutely destroy Switch launch numbers. There could be spoiler tactics. Maybe a Vita price cut or a new model that massively increases battery life and features wireless tv out dongle. A minor low cost technical revision for a console that already has wide support and may cause others who like the Switch format but would prefer the cheaper price and large software library of Vita.
