I mean lets operate from a basic assumption that because it's a Nintendo portable it will sell enough eventually to be profitable and sell at least 40-50 million or so and that's enough for Nintendo to make a Switch 2 or whatever it is they want to do.
Beyond that though it doesn't really matter that much how much further it goes really. PS4 and XB1 already have almost 100 million shipped already and nothing is going to stop them from shipping 160-180 million, factor in Steam/PC on top of that, that's over 200 million users, third parties are obviously going to have no choice but to focus on this base of players before the Switch base. It's just how it's going to be.
Switch will get 3DS type support which is OK, but that's unlikely to change much regardless of if the system sells 40-50 million or even 70-90 million IMO. It'll be mostly the same types of games.
So at the end of the day I just don't see much difference here, Switch kinda has its place in the market, but its unlikely to upend the market, it's not like it's going to magically start pulling third party games away from the PS4/XB1 no matter what it does and portable centric Japanese franchises like Monster Hunter and Yokai Watch were going to be on Switch no matter what, so nothing really changes much there.
Our end user experience with Switch from a gaming perspective is not likely to be altered much by sales IMO unless something incredibly dramatic happens (bad or good).