To be fair, though, do we actually know that of this Hikaru Sulu? I think it would be a nice touch.
That's a good question.
Was it ever stated that Sulu was or ever had been in a relationship with Demora's mother?
It's been a while since I've seen GEN, but I think the Kirk just asked "When did Sulu ever find time for a family?" If Sulu is gay, then Kirk is just affirming that "Sulu, his husband, and their daughter are a family."
I can't think of any other instance that specifically suggested he was into women. I know he sort of flirted with Rand once or twice, but you could just as easily chalk that up to being friendly.
If they do decide to have a gay character (and it really is time), Sulu is the obvious choice. George is so popular now, that I think much of the general public thinks Sulu was
gay. I know I've had to correct people on that more than once.
And just from what I've seen of him, I think Cho would probably jump at the idea. Hell, why not have a little fun with it and have Penn play his partner/husband? I say that jokingly, of course. But the two had such great bro chemistry, there's a good chance that would translate romantically.