Not to mention he would piss off the Bolt x Hinata clone fanbase and Pierrot themselves(whom also ship anything remotely NaruHina-esque) if he made Boruto gay or bi. This would also re-ignite the NaruSasu fanbase into re-examining their relationship and make the assertion that Naruto really was in love with Sasuke and Hinata was just a cover, which would piss NaruHina fans off. Likely, any potential LBGT characters that he may or may not introduce won't be the current characters but ones yet to appear in the manga. And like you said, the manga's pacing is so glacial and in decline in terms of sales that it's likely to be cancelled before anything truly develops and that's assuming that this isn't just lip service.
The only character that matters if he gay is Nail but all that does is make us go, "oh he is gay," and add a bit to his relationship/conflict with Bolt. But, again, look at the comments they ain't pairing Bolt/Nail -the character the writers care about because he is their creation- they are pairing Bolt/Cups -because he is in the anime and the fans they have left are more anime watcher then manga readers-.