... Maybe.
That's an interesting question.
I'd like to say "no" regarding Sera, because I think an openly selfish, money-driven, insensitive, anti-mage, anti-elf, anti-intellectual "I just want things back to normal so I can go play!" man-child, who has literally the intellectual and emotional maturity of a 10-year-old, and who constantly draws butts, makes farting sounds, plays pranks on people, and is in all other ways a complete ****** wouldn't be too popular with the ladies. I'd like to think most fans would be equally (if not more) put off by a male character who is so crass, selfish, racist, and immature. (In fact, I think Sera's immaturity would be even less well-received by fans if male than female, because I can see male and female players alike being being like, "Dude, you're a grown-ass adult. You aren't 13 anymore. Act your ****** age.")
Solas, probably not. I actually don't think Solas is that popular outside the mage fans and the intellectual-loving fans, but part of what gives him a boost for many women (in my view) is how polite, cultured, refined, and intellectual he is. With the standards of manliness in most games and movies being that men must be beefy, hairy, muscular, athletic, and/or physically active (read: most Dragon Age male companions before now), a huge part of Solas' charm seems to be that he's like the refined professor you don't see often in this medium.
However, women and female characters are generally expected to be more intellectual anyway, so that wouldn't earn her any brownie points. In fact, a female character who constantly talks about and/or lectures characters about the past would be seen as this boring, haughty, elitist, a "God, you think you're so smart" know-it-all, gives long boring lectures on things players don't care about, etc... much like how many players view Solas anyway.
So, yeah. I don't think it would make too much of a difference if Sera was male and Solas was female.