At this point I see Switch hitting 157m-158m lifetime. If next gen comes out next Spring I could see it being at 153m by the launch or end of that Spring quarter, passing 155m by end of 2025, and sell a couple million more after that. This is assuming there is no price cut to boost sales, as without a price cut OG and OLED Switch sales should very quickly die out once next gen starts since people will be able to pay just a little bit more to get the brand new system, so I except pretty much only the Lite to be selling mostly to kids once next gen starts.
However if they were to do a $50 price cut across the board next year, along with dropping a bunch of first party games to $30, I could see Switch having a possibility to hit 160m as that could make a $250 OG Switch or $150 Lite with cheap games a possible pickup for Sony/MS/PC gamers or budget gamers who haven't yet picked it up but would be interested in playing some of Switch's gems at a low price.