Sex
With Quatre, you never know. I mean, i want to say it will be sweet and loving, but hell, Quatre could be into S&M!
Marraige Prospects
Quatre is the kind to want to settle down, and he may even be able to convince Wufei. If they do get married, they must be in love or Quatre never would have allowed it, and thus they would have a happy life.
Hints
Absalutely none that i can think of. If you can, email me.
Do they even talk?
Overall
It really could work. Not commonly thought of, but i think that if Trowa were out of the picture Quatre may notice Wufei in a not so friendly way. I think their personalities would work well together once Wufei gets past his shell of insicurities.