Yeah a Switch Pro just wouldn't make much sense, Nintendo's audience don't care about graphics the way that the Playstation/Xbox audience do, and doing it to get more third party ports would be pointless as third parties aren't going to be bothered porting to a small fraction of the userbase, and again, AAA ports aren't what's selling the Switch anyway.
It wouldn't be worth their while, they're better off waiting another two years or so and releasing a full blown successor.
Well a successor is a lot more than two years off. Two years would be cutting the Switch off very early. Even 3 years would be cutting it off a bit early.
And um yes Nintendo's audience cares about graphics. I mean yeah you're right not in the way PSXbox audience does where they seem to take graphics as the most important thing sometimes, but just because its a handheld doesn't mean people don't want good graphics, good resolution, good fps. We just know its a handheld, so great graphics on the Switch are gonna be not quite as great as those on home systems. Also absolutely Nintendo audience care about third party games are you kidding. I'm sure a lot of the audience would love to have full good versions of AAA third party games on the system. The fact that those games barely ever make it to the system is not at all the same thing as not wanting them on the system. AAA ports don't sell the Switch because they don't (or barely) exist on the Switch and when they do they are either a generation old or degraded versions from more powerful hardware. First party is what sells the Switch because Nintendo is the only company that makes new AAA games for the system. Obviously if third parties actually built new AAA games for the Switch there would be a lot more interest. The main reason to not do a mid generation upgrade is because it'd split the userbase, because nobody wants that.
My suggestion was more if they did a mid gen upgrade to a bit more powerful version that could play current gen games decently without a lot of changes and graphical sacrifices needed, that would maybe get more developers taking the leap to port AAA games to Switch, but those games just wouldn't run great on the original Switch systems so they'd be better on the upgraded model but obviously they'd still have to run on the standard power systems, meaning there would be no split of userbase, but you just had to buy the upgrade if you wanted to get the best AAA experience.
Anyway, no doubt much more likely the Premium Switch whenever it comes out will be at best a slight power boost and then bigger screen and whatnot, like Nintendo always does with its upgrades. Late 2021 or early 2022 I think would be about right timing for another version, as that gives it at least a couple more years to sell before next gen.