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.
That's a lot of wasted money if they're this close to releasing it, and 20% would be 100% worth it.
They could still release a new console two years later, believe the same happened with the PS4 pro and Xbox One X.