If the Switch is selling like gangbusters without the majority of the AAA third party support on PS4/Xbone, would it really change that much with PS5/XB series X?
Outside of The Witcher 3, Rocket League, MK11, etc., those ports not common and even games that appear like no-brainer ports (i.e., Persona 5 (OG or Royal), SFV: CE, GTAV or even GTAIV, COD4MW (the remaster, not the 2019 reboot), Madden, etc.) are pies in the sky at this point.
It's a frustrating thing because the Switch is successful, but most higher-profile developers are giving little #$%^&. Fortunately, the Switch is doing its thing and selling really well. Even in 2018 when the Switch had a "down" year of only Super Mario Party, Pokemon Let's Go, Mario Tennis Aces, and Super Smash Bros. Ultimate, it was still selling well against games like Spiderman, God of War (2018), Monster Hunter World, and Red Dead Redemption 2 that were sold on the other consoles.
So what if the next-gen consoles are 10x (maybe exaggerated?) more powerful than Switch? If the Animal Crossing version of the Switch means anything, is that games matter and there are people out there that Nintendo can market their console towards.
If power and specs were the main reason consoles have to be successful and maintain their success, the Nintendo DS wouldn't be the 2nd best-selling console of all-time nor the Wii wouldn't have reached 100+ million and reach a completely new audience.
The main thing that would be a problem is if third party developers end up not taking advantage of the huge install base of the Switch (looking at you Capcom and, to a smaller extent, EA).