No doubt a new Switch with updated power is coming at some point. I would think it won't be branded as a Switch Pro as Nintendo would likely discontinue the current Switch and run with the Switch "Pro" and handheld only switch variant when that happens. I would expect it to be significantly more powerful than the current switch and to come out in 2020 or 2021. I see the switch concept lasting quite a long time with several updates and new variants released. I just don't see what Nintendo would do hardware wise if it wasn't continuing down this same path. It would be nice if they came out with a console only version that was similar in size to the Apple TV. This version could have more power as you don't have to cram it all into a handheld form factor you could likely run in hotter.
Assuming Nintendo sticks with mobile chips for let's say another 8 years what will the landscape be by that time for a traditional console? The cloud will likely have reasonably high adoption rates by this time and there are diminishing returns on power. I just don't see Nintendo going back to a traditional console ever again. If and when the Switch concept loses momentum who knows what Nintendo will do at this time.