What I would like to see: Vivienne/Varric.
What I expect most to see: Either Vivienne/Solas
(But I can also see Vivienne/Blackwell happening).
With all four of these characters, I can see reasons why we could/couldn't romance them, especially with us hearing that some are "too busy for romances". They all in some way or another seem to potentially fit into that context? I'm definitely probably just thinking about it way too hard.
Vivienne sounds like she's so poised and mindful of how she's perceived, that I can imagine her not wanting to indulge in romance while she's helping out the inquisition. That being said, I would love to have the chance to romance her, and it'd make sense for her to be an LI if there is going to be gender-equal romances. Seeing an icy personality that can hurt you with words just as much as magic be able to melt her personality down for a romance, would be fascinating to see. I would love to see that.
For Varric, it would be amazing for everyone who's wanted to romance him to be able to. But in the comics (and some of his dialogue in DA2), it sounds like Varric might have a reason to not want to be in a romantic relationship with anybody. But I also could be entirely wrong. In fact, it would be rather adorable to see his character progression if he got to be in a relationship with the Inquisitor, especially given the little we found out about his past in the comics.
Meanwhile, Solas has spent his entire life on his own (or that's what it sounds like), and his life has been very dedicated to the Fade and unraveling it's secrets. Does he have time for romance? Maybe not, or maybe it's something that's slightly foreign to him (or maybe not, I don't know him well enough) but that doesn't mean that he's not willing to try. That would be a cute approach for a romance. Same goes for Blackwell. He seems very proud to be a Grey Warden, and I can see him having an earnest romance just as much as I can see him not wanting to get involved with him due to his inevitable short life.
I'm also curious to see how they go about sexual orientation for these last two LIs. For instance, Vivienne; I personally really hope that, if she is a romance, that she's bi. Both because...I'm lesbian, and would love to have a chance to romance her as a FemInquisitor. But also because it would be nice to see a straight/bi/gay ratio so that different orientations have a similar amount of romance options. But the developers have also stated multiple times that the romance options are designed because that's how that character's orientation is, and they're not designed because they need "a certain amount" of gay/bi/straight LIs.
At any rate, I'm excited to hear the last two romance options. The ones who I've thought might be a romance, are. Now I (obviously) don't have a clue and hope we find out the rest very soon!