How about this:
In the future, nobody will care! I mean, only a handful of major characters have gotten their sexuality defined in ANY way, let alone had a romance on-screen. Considering that, to create a gay character purely to have a gay character would be terrible writing. How would it affect the story, unless you're making the story about how a gay character's gay?
I think the gay issue should be a complete non-issue in the future, like Picard's lack of hair. Like Roddenberry said about baldness in the 24th century: "Noone will care."