The mobile versions of Fortnite and PUBG are always an option. Not sure what the lowest spec phone is that could run the game. I tried to play PUBG with my stepson on mobile with his throwaway phone for games, but it is not compatible.
That is another reason that mobile meshing with console games does not guarantee a Switch version. An Iphone 16 might play games that phones today, or the Switch for that matter, wouldn't be able to run.
Nintendo won't stick with the Switch forever. They'll upgrade eventually.
This is true, however that will likely be further into the lifeapan of the PS5 and X(2). If they follow the business model for Switch, which makes sense, and release a Switch 2, it will likely have a similar power gap with the other two that we see today. Also by then, the PS5 would likely have a commanding lead to where the damage will have already been done, unless Sony drops the ball elsewhere that is.
Now if Nintendo were to get into the market of launching beefed up consoles, which likely will not happen, but IF they do...things could be a little different. However it would still result in them needing to launch it closer to the PS5 rather than later to make the biggest impact. If they did this, I could see Switch becoming a handheld that can be connected to the TV and officially replacing the 3DS, which would keep them from shutting out millions of Switch owners early.
Now if this happens...well then things get interesting as we would now have a 3rd beefy console for MS to crossplay with. However based on Nintendo's history and how this requires a number of factors to line up...it is still possible...but highly unlikely.