Not to be taken seriously.
Relena and Heero? He protected her from Oz during the trial, and after the war ended, they dated responsibly for a few years until they were both of age, and then Heero finally decided he was tired of being a soldier, and they got married.
Quatre and Trowa ended up having a huge fight, and they reconciled after a year and a few months because they just couldn't live without each other.
Duo and Wufei, to everyone's surprise, continued to bicker/banter about many things, but were also happier than anyone had seen them. They joined the Preventers for a while, and then, after a few complaints about a certain somebody's insane humor being a tad inappropriate for diplomatic work (which they should have known), Duo changed to head mechanic and test pilot for the Preventers, while Wufei dropped from active status to teach the new recruits so he could be with Duo. They ate good food, drank good drink, and were generally quite happy.
All the pilots and Relena reunited every Christmas and occasionally on a birthday, and generally kept in touch. Wufei still can't believe Duo dressed up as Relena, and to this day, Quatre still has dreams about Duo in a dress.
Eventually, they all get old and die. The end. Happy now?