ok, you have some good points there, hell i'll give you the benefit of the doubt that Switch could MAAAAAAAAAAAAYBE sell less than the PS4, but i mean... that's like, super unlikely.
Just look at facts and current trends. "no one know what's gonna happen with Switch" ok but like it's selling at Wii/NDS level of peak 2008/2009, AND IT HAS SHORTAGES, which mean domand is actually higher than the numbers we are seeing right now.
Of course using some logic someone would expect Switch sales to stay very stong for a while. and considering that this year is pretty much safe to say Switch should end at around 80 million (probabily more than that but i'll make a safe bet), Switch only need another strong year to pretty much be guaranteed to outsell the PS4.
Unless you expect PS4 sales to better than expected and reach something like 140 million but this seem kinda crazy at this point, Sony looks like is giving up with PS4 production and focus on PS5. Even 130 million seem extremely hard.
I mean, again, nothing is impossible but at this point i'd give PS4 <10% chances of winning against Switch, and i'll be extremely surprised if this happen.
EDIT: For the record, i think Switch will do over 150 million... so even with the best scenario for PS4 i'd still predict Switch>PS4
Sure, the Switch can do it, I just don't think it will. Think 2020 is the peak year, it'll still be going strong next year, and then sales will start declining fast, but maybe I'm wrong in thinking that. It just seems to be the rule for Nintendo home consoles, but yeah, the Switch isn't really that. Kinda get the feeling that we'll get another Mario, BotW 2, and after those two we're not gonna get more major hardware-moving games.
I'm also thinking the PS5 will have a slow start, meaning the PS4 will continue to sell well for at least another year or two.