Yeah... well this is just one theory that very silly theologian-types bat around. The serious theologians waste no time on this question since it doesn't matter and there's no real way of knowing. The basic premise is that there should be no need for things that pertain to the human body, since we would have transcended that form. So people often think that there won't be hunger, but you can eat if that's something you enjoy. The Bible actually specifies that there won't be marriage in heaven, but it's silent on sex. So a complete open society, hooking up whenever and with whomever you like, would be a theoretical possibility, but only if heaven came with a solution reconciling the problems of rejection (will I feel emotional pain if a girl doesn't want to sleep with me?) and individual autonomy (shouldn't I be able to say no to sex if I don't feel like it?).

But then, the larger point is transcendence of the human form. People who are presently in this form are generally ill qualified to predict the desires of another form. It would be like a caterpillar who had never even seen a butterfly pontificating on the perils of flight, or bemoaning the butterfly's inability to form cocoons.