Upgraded switch like the X or pro, and it will NOT be this year. Late 2020 or early 2021

There will likely be a release next year for the Switch Pro.  Switch Mini is coming this year.  Pro will feature a higher resolution screen and enough additional power to allow more 3rd party games.  It will not be an entirely new system, but developers will be allowed to make a decision on if they want to support the base Switch or if their game will need to use the extra power.  Nintendo will sell the Pro piece-wise.  Some skews with controllers, some with docks, some with only the body. The body only offer, without controllers or dock, will sell for $200 for those who want to upgrade their Switch.  The controllers will be the same design and similar cost individually bought that they are now.  The Switch Pro skew with controllers and dock will be the original launch price of $300, and the original model will go down to $200 with controllers and dock, until those skews sell out.   While they will likely make every skew, original and new, in mass quantities for next holiday, I'm not sure if they will continue to make original skews after the holidays once they are gone. I doubt they will. They originally had planned for Metroid Prime 4 to launch with it, bundled with it's own Labo VR variant, but due to the huge development delay, Nintendo will change the launch title to market with its features.  First party games will be made to support all Switch versions, but may have some adjustments to take more advantage of the Pro features.  I'm not sure how long into the Switch Pro's lifespan they will continue that trend.

I still believe that we see a cheaper SKU without dock this year to replace the 3DS and please the handheld customers and next year we get a dock with additional power for the ones who primary use the console in TV mode and to have a chance to somehow compete with PS5/Nextbox and get further third party support for more demanding games.

I have a hard time believing Nintendo would risk resetting their userbase even when the Switch 2 finally releases. Rumors suggest the next Xbox and PS consoles will be BC with the current gen, so Nintendo forcing everyone to restart would just be a sore spot for marketing.

But as for the OP specifically, I seriously doubt it would be a brand new system that breaks compatibility with the Switch if it's called the "Switch Pro". That would be super confusing, and be unlike any other mid-gen upgrade that they've released previously (Game Boy Color, DSi, New 3DS).

Super implies significant improvement, U means nothing.

I'm not sure why an upgrade isn't realistic. Gameboy Color, DSi & New 3DS all had improved specs over the base models.

Doom Eternal and Mortal Kombat 11 already demonstrate that "Switch won't be able to handle any 2019-and-beyond PS4/Xbone games" isn't true, and it's highly unlikely they'll be the only ones it'll get.

And the flaw in your "Nintendo must release a next gen system in 2021 at the latest" logic is that there is no good reason to do so simply to get AAA third party support, because Nintendo systems don't need AAA third party games, they can sell just fine without them.

sorry, I got a bit confused. I meant the new 3DS which was an incremental spec increase that had marginal improvements over the base model, much like the DSi and Gameboy color. I think we're much more likely to see that.

Gotcha, I had a feeling that's what you meant but wasn't quite sure. I think they might go a little further than that, like a middle ground between New 3DS & PS4 Pro level upgrade but ya I dont see any massive upgrade happening.

I really think 2 redesigns using the Tegra X2 make sense. X2 can either have double the performance or equal performance with half the power draw of the X1.

With this you could have a somewhat smaller, sleeker sku with better battery life and the same performance of the current model while also having a somewhat more powerful sku with a 1080p screen and better performance.

I guess it would be similar to 2DS vs New 3DS XL.

Switch Plus or Super Switch. Sony called dibs on "Pro".