I doubt Nintendo would be introducing a new more powerful model with 4K graphics in 2021 if they weren't worried to some degree that the Switch could have problems with running certain games in the years going forward or the system would begin to look too dated.
Cultural phenomenons Fortnite and Minecraft do run on the Switch but there's no guarantee at all that the "next big thing" might require a spec that the current Switch can't hit. Whatever the next thing might be something that's built for a modern high end PC or PS5 and that would be a problem for a Switch version.
Furukawa strikes me as a different kind of president who isn't impressed by success in the moment because he's said that can very fleeting and change in an instant. That's the exact attitude Nintendo has needed for ages, if they had someone more on the ball like that maybe certain painful lessons would not have needed to have been learned. Being passive and drunk on your success is a recipe for getting your ass handed to you eventually.
The other thing is adopted relatively cutting edge tech like DLSS is kind of unique for post-1990s Nintendo, it will be interesting to see how different hardware development and developer outreach is under Furukawa.