The historic basis of relationships was for procreation and child rearing purposes.

Um, no. The historic basis of relationships was allying for a common goal. Or, did you mean sexual relationships. In that case it would be helpful to define what you mean by "sexual", especially once it's no longer connected to reproduction.

In the future I expect that to not be the case. either with designer-babies, or just plenty of non-natural birthing solutions as to make the next generation make-able without needing to go through a regular-family structure.

That would turn humans into a eusocial species. That change is likely to have a much bigger and more important effect then whatever ways of creating superstimulus by non-reproductively rubbing genitals are socially allowed.