I'm not sure if anyone has had this take, but I now believe Nintendo cancelled the Pro. I think they were expecting Switch sales to be lower last year (by a lot) and not even close to what they have been this year, which would warrant a Switch Pro. They don't release new hardware, I don't believe unless their current hardware sales are tanking or at least diminishing greatly. We are still seeing roughly 400k Switch's sell every week and we are only in the second quarter, so why would they need to release the Pro at this point at all? To play some more games for the 10-20% (max) of their userbase that would bother to get the upgrade? I think not.
If the Switch upgrade is actually a successor, then it's going to release between 2022-2023 and all 1st party games are going to be multi-gen for the first couple of years like what Microsoft is doing with their new console. In that instance, it will basically act like an upgraded model while getting 3rd party games that can't run on the Switch.
If not that, then we aren't getting a Switch successor until 2026 because after all of Nintendo's major teams release games in 2022-2023, it's going to take them until 2026 before they're ready to go again.