The Teen Titans have gone through numerous changes over the decades, from lineups to locations, but since his introduction, Beast Boy has been one of the team's few constants. The green-skinned shapeshifter has been through a lot, and there's been many things that have defined him in the years since his existence. They're hard to ignore, too, from his veganism to his love of jokes. However, there's one part of him that hasn't gotten so much attention from those who write him: Ol' Garfield Logan has some leanings towards being a queer character.
It may seem incredibly random to say, but when you step back and think about Beast Boy across the various forms of media he's been in, it makes sense. Beast Boy is an incredibly romantic person at heart, someone who loves to love and yearns to be loved. Both Terra and Raven are proof of this, as they're the constant romantic interests each iteration of his character. With both women, he's wound up playing the role that women normally do in these stories: He's the one who has to appeal to their humanity while they're the ticking time bombs. You can see this most famously in the Teen Titans cartoon -- his constant emotional appeals to Terra's humanity inspire her to turn on Slade, and Raven only really begins to open up emotionally because of him. "You think you're alone, Raven," he declares, "but you're not." His occasional dips into harmful masculinity aside, such as when chemicals drastically altered his personality into more of an alpha male type, he's a sensitive soul with love for everyone in his heart.
And, of course, there's Cyborg, which is where Teen Titans Go! comes in. Though the show doesn't really address Beast Boy's queerness in any real capacity (There iss a clever Martian Manhunter joke where he completely misunderstands the name, but accepts the title with a wink.), there's still something going on with the character. The series has firmly established that Gar and Vic are a package deal, leading to some of its best comedy moments featuring the duo. Just as the show isn't afraid to stoke the powerful flames of Beast Boy and Raven, so it goes with him and Cyborg. In two separate episodes, Beast Boy is stuck in a classic romantic comedy plot wherein he goes to great lengths to get Cyborg an expensive gift for his birthday. (Cyborg, both times, flat out says that he'd prefer something simple, but being who he is, Beast Boy doesn't listen.)
More recently, there was an episode that devoted itself to celebrating their friendship as though it was an anniversary or birthday. Not only does the episode involve a tiny creature that serves as a personification of their relationship, it had direct references to Top Gun (a film that is unashamedly queer) where they played volleyball with their shirts off and slapped each other's butts. Yes, really. And the other Titans went out of their way to recreate their relationship, like something out of a romcom, because they ship those two so much.
With Beast Boy as a main character in the upcoming Titans series, this is as good a time as any to officially make him bisexual. If the show's version of our green-skinned hero will be anything like the comics, he'll be insecure thanks to his appearance or his past. With Greg Berlanti involved in the creation of the series, it's safe to say that emotional melodrama will be a big part of the show's proceedings. Gar is a great vehicle for that melodrama. His insecurities and desire to be loved are perfect for a character arc that follows him coming to terms with his sexuality. The other DC shows all have at least one LGBT character, but they're all overwhelmingly white. With Beast Boy being played by Asian actor Ryan Potter, him being bisexual would be welcome in more ways than one.
Again, it's likely that no one at DC has ever really realized they have a queer character on their hands with Beast Boy. The Teen Titans as a group exist for characters to come into their own identities, and Beast Boy has never really had that chance afforded to him as Robin or Starfire have. Having him come into his sexuality would be the first step in giving the typically funny Titan a serious move forward.