I don't believe a more powerful Nintendo Switch is very likely. Maybe a new, more powerful console released by Nintendo 3 or 4 years from now, but I wouldn't expect backwards compatibility with Nintendo Switch titles unless it's either powerful enough to emulate it or there's incredible development in portable, ARM technology in the next 2 or 3 years.
As mentioned in the thread, Nintendo did release more capable revisions of their hardware in the past: the DSi and the New 3DS. Exclusive titles did exist, but there were better reasons for the revisions: the DSi allowed one to download DSiWare games onto an SD card, and the New 3DS brought face-tracking 3D (that Miyamoto said had been planned for the 3DS from the get-go) and the C-stick to replace the Circle Pad Pro. Moreover, the Switch was released in 2017, merging the company's handheld and console divisions into one. To release a new system so soon would be cannibalizing their own product, especially now that they just released the Switch Lite.
That said, the XBOX ONE X and the Play Station 4 Pro are far ahead of the Switch performance wise, and both feature x86_64 architecture CPUs, making it easier for companies to port PC games to it and vice versa. The XBOX Series X and Play Station 5 will likely stay on the same architecture, and thus graphically impressive AAA titles will likely appear there first. We're already seeing how those titles perform on the Switch with the watered down albeit impressive ports. With the release of the two consoles in late 2020, the Switch will likely become an indie platform much like the Vita did, despite the first party support from Nintendo with which Sony didn't bless the Vita.
Perhaps Nintendo doesn't want to compete with Sony and Microsoft directly as they had done in the past, but unfortunately third party support goes away as quickly as it comes. I just hope they have many more first party games planned for the Switch since that's what I like to play and I just ordered mine.