There's still no indication that third parties would be any more willing to develop for a Switch Pro than they are for the current Switch.
We'll see, you can't know that because you can't read the mind of every single third party developer.
Embracing a PC like setup where there is no real generations personally I think is smart and in the *long run* consumers will also see it as a positive and not want to go back to the old model. And getting in on that "Pro money" model that Apple/Samsung/Sony/Microsoft all make good $$$$ from is something Nintendo is going to end up doing most likely regardless of a few people on an internet message board complaining about it.
The reality is a 2-3x style "Pro upgrade" of a Switch simply would allow a lot of games that would be a real pain in the ass or impossible to port to the old Switch to become reasonable feasible on the Pro model. Some third parties will likely bite on that proposition and Nintendo won't stop them.