First off, you only talk about sexbots in your post and use one porn video as definitive proof that no technology could ever replace human relationships. That's a pretty massive logical leap there.
Now with that said, sex bots alone will never replace human relationships. Even if you could get them to feel like a real woman in a tactile sense (which probably wouldn't be too hard actually), without AI, they would be nothing more than large and expensive masturbation devices.
On the other hand, AI could definitely replace human relationships. It would have to be sentient though, or in the very least it would have to definitively pass the turing test (whether or not it would be considered sentient at that point is a complex issue).
The question is when will we have AI that is sentient(passing) and is legally available to the general public and at a semi-reasonable price. It could be anywhere in between 15 to 100 years from now that sentient AI exists at all. Then there's not only making it so that it could be semi-affordable to the masses, but also the legal issues. Obviously the government would have a lot of concerns about what the masses would use AI for, it potentially being used for cyber attacks or terrorism, etc. And that issue wouldn't be as simple as just programming it with Asimov's 3 laws of robotics. Then there would obviously be people on the cultural far left that would want it banned.
All that said I think barring a catastrophic eotwawki event, at some point in the future all of these issues will be sorted out and AI will be available to the masses and will gradually replace human relationships altogether (it's not just incels that would opt to have romantic relationships with AI).
The question is, how long will it be until we get to that point? It will probably be at least 30 years and there's a good chance it won't happen in any of our lifetimes.