Sure, go ahead 
*cracks knuckles*
Okay, we know from BaBR that all race/gender/sexuality combos have at least two options. We know Iron Bull was race-gated, and that his writing was done before Epler changed that. (They specifically said they had to "go back and remove" dialogue after he was done with the race-gate.) So it's a pretty safe bet that, from a balance perspective, Iron Bull was treated as if he was race-gated. So we've got at least one guy who's into women, and at least one guy who's into men. Possibly the same character. Nothing too surprising.
We know one of our known LIs is race-gated. So we still don't have a solid 2/2/2 split. If Cassandra or Sera are race-gated, Vivienne's definitely in just to cover the gap. If Cullen or Dorian are race-gated, that might not mean anything, since they could be balanced with Iron Bull and our mystery third.
Here's my speculation, though. I don't think Sera or Dorian are race-gated, because they're the first same-sex-only companions BioWare's had in a while, which is kind of a big deal. I don't think Cassandra's race-gated, since she was described as "secretly a romantic" in her character interview. (Which might not mean anything, but they hinted at Iron Bull being race-gated during his interview, so it's something to go on.) That leaves Cullen, which makes sense, since he's had unfavorable things to say about dwarves (DA:O) and qunari (DA2). The thing is, if Cullen is race-gated, and Iron Bull was race-gated, then that leaves both characters probably blocked from dwarves. That would leave straight female dwarves with zero options, which would mean the last two options are both men. You'd need to cover every eventuality Cullen and Iron Bull miss, so that would mean either one straight and one bisexual guy, or two bisexuals.
Judging from Solas' VA's comments, he's probably in right now. He's also probably not race-gated, like I mentioned earlier. And since the last character needs to be race-gated, and I don't think Blackwall is, that'd leave Varric as our second.