I've only recently come around to thinking it will hit 110 million. There's a lot of reasons that it could not hit more than that. Lack of price cuts, lack of new software from Nintendo, production delays/complications, or somehow overall decrease in consumer interest. The lack of price cuts hasn't been a problem on Switch yet. But if we're going into 2022 or 2023 with Switch still at $300 and Switch Lite at $200, I think there will be a problem.
I don't see that happening, at all. The two variables for me are software support and current economic climate. Nintendo seems to recognize their missteps with the Wii and having to produce games for two very different platforms (handheld/console) so they're likely to do their best to continue supporting this system for quite a while. They're even saying as much right now. As far as the economic situation, it seems to me that the videogame market is mostly recession proof. The question I have is whether it will be depression proof, and that's something that certainly the US hasn't had to deal with for almost 100 years. Likely, though, some sort of stimulus package will ensure that people have a few dollars in their pockets no matter what, and consoles have always provided some of the best bang for your entertainment buck. And escapism may be our only refuge in the coming years.
But as far as price cuts, there's so much meat on the bone with the Switch that at some point in time (when sales falter) dropping $50 or adding in a brand new Zelda or Mario bundle will be a cinch. The $100 price cut will be an amazing boom for the system and could see a lot of families double or triple dipping on the system to make sure every kid (and parent) in their household has one. This wasn't something that was very common with the Wii, and approaches the more personal nature of the DS.
I'm terrible at these long term predictions, but I can certainly see the Switch selling 120 million...and the OP is right to shoot for 130 million.