I wonder would Nintendo require you to buy their online pass in order to play gamepass. Could be a worthwhile trade off.
If they do this I believe the xbox will sell less as the exclusives will be available on Switch and pc.
Not sure about Switch online. With such a move Xbox Live available for Switch would be very possible.
And I not necessarily think this makes the Xbox-console obsolete. Streaming is still far away from being as good as having the possibility to play a game natively. So maybe Switch-owners like the games they play via gamepass but want them lag-free and invest in a Xbox.