Based on just the hardware alone (streaming sticks/players) which can decode x265 and CAN’T decode AV1 that is simply not the case.
We only have history to show the way…
To think that AV1/2 etc will be so good that 100s of millions of consumers will want to replace their devices that work perfectly well is just ignorant - plus it would be environmental suicide.
AV1 isn’t THAT much better than x265 anyway.
Both can and will co-exist for long after AV3 has been released. That said, I do think AV1/2 will be the next defacto standard and x266/VVC (Versatile Video Coding) will have a difficult time gaining any traction against a free well-supported competitor.
We can check back with each other in 10 years and see what actually transpired. Otherwise, our gabbing about future standards is academic.