Didn't Star Trek already try to tackle this issue twice? First in the episode where Riker falls for that one person from a culture of genderless monosexuals, and again when Jadzia Dax fell in love with the new carrier of a symbiote who was previously bonded with the spouse of one of her previous hosts? Granted, that depiction was still of a persecuted minority, but it's something at least.
The reason we know that Star Trek "looked forward to a brighter tomorrow" with regards to race was because it depicted people of many different races on screen together as equals. The thing about race, though, is that it's always something that's right there for people to see, so it's easy to show people "hey, this isn't really any big deal for us, we're all just people."
Sexual orientation, on the other hand, has no such obvious external indicators (unless you happen to make a gay character a queen-type, which would be a massive
disservice to te LGBT community). Writing a "normal" gay person while at the same time trying to get across the fact that this person is gay is tremendously difficult, because you have to make it known without drawing attention to it. And trust me, some people interpret ANY outwards signs of someone being gay as an overt attempt to advertise the fact, even something as simple as a gay person telling their partner, "see you after your shift."
The other thing that makes it difficult to depict properly is that Star Trek's depiction of romantic entanglement has always seemed like a bit of crutch, an easy fallback mechanism to write filler stories. Yes, relationships happen, but considering the franchise focuses on what is technically a military organization, it has always spent too much effort on it, and it generally comes across as more of an attempt to placate "shippers" than as a way to orchestrate personal growth. Combine this less-than-stellar track record of relationship drama with a hot-button issue like sexual orientation, and I just don't see it ending well.
2 cents deposited.