Keep in mind the Switch rarely gets 3rd party, multiplat support outside of indie games. Of the big 30 or so AAA games released each year, the Switch gets maybe 4?

I don't see this changing

A combo of Switch Lite and PS5/XboxSeries could be a serious scenario in the future. No one will care about the docked version because it's simply too weak and because of that it is wasted. But ports of older games will continue and we should be very thankfull for that.

Some of the multiplat games Switch missed in 2019:

Ace Combat 7
Life is Strange 2
Resident Evil 2
Kingdom Hearts 3
Apex Legends
Far Cry New Dawn
Metro Exodus
Anthem
Dirt Rally 2
Dead or Alive 6
Devil May Cry 5
The Division 2
Sekiro
World War Z
A Plauge Tale
Rage 2
MotoGP 19
F1 2019
Madden 20
Control
Borderlands 3
Ghost Recon Breakpoint
Grid
Plants vs Zombies Battle for Neighbourville
Call of Duty Modern Warfare
Need for Speed Heat
Star Wars Jedi Fallen Order

Yes Switch is already missing a lot of third party titles, so PS5/XSX making ports less viable is going to make very little difference.

That's what people said about the Switch three years ago; it won't sell because it's too weak compared to PS4 Pro and Xbox One X. Now, it's one of the fastest selling systems ever.

Tons of systems and countless games have proven that having the best graphics just isn't that important to the average consumer. If it was, the Xbox One X would be the top selling console right now, the Wii would've failed, and games like Minecraft and Roblox wouldn't be crazy popular.

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).

Did the DS or 3DS not get support because of the PS3 or PS4?

The Switch will continue to have their combined handheld and console IPs pooled together on one platform. The Switch will continue to be the indie platform (which is 3rd party) of choice. Japanese 3rd party support will continue to be strong on Switch, as most of those developers do not make demanding games to begin with. Plus the Japanese market is perfect for Switch, as seen by console sales and their portable focus. AA games will also see Switch releases from western devs, as the install base is too big to ignore.

The only thing the Switch will see slow down will be AAA 3rd party games, which are largely overrated to begin with these days. For over three years, it was certainly nice to have games like Outer Worlds, Witcher 3, MK11, DOOM, DOOM Eternal, Wolfenstein 2, etc available on the go. However this made up a small fraction of the library and will likely just be replaced with more 3rd party collaborations such as Astral Chain, Mario Plus Rabbids, Daemon X Machina, and Octopath Traveler that you can play no where else (save for the odd PC release).  And finally, the fact that some of those bigger games I listed above runs on Switch at all give devs and entire generation of games to release on the go should they feel like it.

So no, the Switch will not lose 3rd party support due to the PS5 and X1S. The library will not suffer, and sales will continue to be strong enough to push it past the Wii.

If the numbers for Switch is like 400Gflops undocked and 700Gflops docked on current then it is more like 20-30x power difference against rumored PS5/XSX.

Yes. PS5 and XSX will waste most of their POWAH on bullshit like 4K and Raytracing anyway. Plus they will use the very same engines as games in this gen. So all you gotta do is turn off dat RTX (nobody cares about that anyway) and drop the resolution and some minor graphical details and whatnot.

That said, it's not like anyone in the world would care about 3rd party shovelware on Nintendo systems anyway. I mean, why should you buy 3rd party software when Nintendos titles are superior in each and every way? It doesn't make sense.

The switch will be fine.

On gpu PERFORMANCE, difference will be around 13-16x.

Different architetures, it isn't just a matter of multiplying FLOPS. There is efficiency, bandwidth, etc.