Things will go on a different direction: virtual reality
Robots are not realistic, and we are ages from building something that can convincingly look like a woman (or a man). Something like "Ava" or "Data" won't be seen by anybody that is alive today, Some people will be game for that, as some people are already fucking sex dolls, but it will remain a "niche"
It will be much easier to build a sex robot or sex machine that is simply proficient in the mechanics of sex, then you hook it up to a VR headset with some porn star scenario.. BINGO! the sex machine will take care of your penis, the VR will take care of your mind.