I've heard some people worry that even sufficiently good vibrators and fleshlights will reduce the amount of actual sex people have. Making a robot that a normal person can fall in love with might be AGI-complete (although some people do get attached to robot pets or form imaginary relationships with anime characters or 'waifu') but even a robot which isn't as good as a human still decreases the need for human company.

Also, is the creation of sex robots a matter of AI, or of creating realistic synthetic skin? If its the latter, and AGI turns out to be really hard, then sex robots could easly come a long time before the singularity.