I could easily argue the opposite way: Once perfect sex becomes something you can easily buy in a form of sex robots, and the practice becomes so widespread that it will be socially accepted by the mainstream... maybe the partner relationships will become better, because people would use them to optimize for other values -- such as being nice to each other, being a good conversational partner, etc.
Has this happened with any other technologically supplied superstimulus?
"Technologically applied superstimulus" is a pretty narrow category, but here are a couple of things that come close enough that I think they're relevant.
My impression is that gourmet food has become more interesting as the need for it also to be filling has decreased (because industrial-scale food production has made adequate food really cheap, much as sexbots might hypothetically make adequate sex really easy to get; "perfect" seems too much to hope for).
There is some evidence that violent video games reduce their users' tendency to engage in actual physical violence.
Speaking from personal experience, finding the right relationship can be HARD. I recently came across a rational take on finding relationship partners, much of which really resonated with my experiences:
http://waitbutwhy.com/2014/02/pick-life-partner.html
http://waitbutwhy.com/2014/02/pick-life-partner-part-2.html
(I'm still working my way through the Sequences, and lw has more than eight thousand articles with "relationship" in them. I'm not promising the linked articles include unique information)