Until someone comes up with something better, since I think we are witnessing the end of traditional generations, I will consider Scorpio and PS4Pro as gen 8.5 and the Switch gen 9 (due to technicality). However, I think this is mostly moot. Switch will be competing with gen 8 and gen 8.5, and of course all the phones and tablets out there as well.
I don't think we will see a new console from SONY or MS for a couple years or even longer, by then we might see a successor to Switch. So would we consider SONY/MS starting their 9th gen and Nintendo starting their 10th gen near the same time? That doesn't seem right.