To me the question is what will third party support be after the next gen consoles launch. Porting Doom and Witcher 3 are huge achievements despite their graphical downgrades. But if systems 3-5 times as powerful as the XB1X become the norm then those ports will become so impossible even Panic Button won't be able to do it.
The rumors of a new upgraded Switch model may help, but the boost in power and new hardware features needed to receive ports of 9th gen games would be insane, practically a generational leap over the current model. I don't see how Nintendo can release an upgrade powerful enough to keep up while not abandoning those who bought a Switch over the first 3 years of its lifespan, since if it released such a model then 9th-gen games that came to the Switch would be exclusive to the newer model. I guess they dipped their toe in that with the Nu3DS, but outside of the SNES virtual console and Xenoblade that had very little that was exclusive to it.