Yeah, that's down to a mix of player preference and writer preference. Based on all the metrics the devs have, the vast majority of players aren't into M/M (see
here and
here for examples where they've said this) and it's not something any of the core staff is super-interested in so there isn't an incentive for them to write stuff catering
specifically to that instead of writing pansexual characters whose content everyone can access and there's
no interest in writing more just to make the ratio somewhat less imbalanced. The easiest way to get more M/M content would be for community writers to, well, write some.
Oh, and on your question about seeing upcoming content, yeah, there's no public repository of What's Coming Next. You can see individual writers' topics where they might discuss things they're working on and comments are scattered here and there around the board, but compiling a list of known projects would be a lot of effort for little reward and there's no guarantee that all the stuff that's
talked about on the board ever gets
implemented so it's the sort of task that's possible but about as appealing as organizing a sock drawer*.
* Unless you happen to have a fetish for organizing, for socks or for organizing socks, in which case I won't kinkshame. Much.