I think the biggest risk towards the Nintendo Switch, is if Nintendo does a 3DS succesor as their now saying they will.
They just have to get the Switch down to 199$ (without controller base, or dock).
And they can sell the Switch as a handheld for those that only want a handheld as well.
Rather than make a 3DS successor, Nintnedo should just make a handheld-only NS that's cheaper and less powerful than the original NS. It could be the NS's version of the 2DS. I'd suggest making a stronger traditional home console variant but at this point I'm seeing the NS as Nintendo's concession that they can no longer compete in the home console market. In fact, when I think of it that way, I get a lot less disappointed at what the NS ended up being.