The story from Ananova says it all:

“A British scientist has been awarded a doctorate for a paper predicting that humans will one day marry robots. Maastricht University awarded David Levy a PhD for a thesis entitled Intimate Relationships with Artificial Partners. The thesis examines human attitudes toward affection, love and sexuality and concluded that the findings are just as applicable to human interaction with robots of the future as they are to relationships between humans of today.”

This may not be exclusively an idea of the future: a German inventor says he has already developed a robot with full sexual functionality.