I’m not sure what the fandom’s opinion is on them as a whole—I expect it’s varied—but my personal opinion is the same as yours: I think that bond of friendship would have been there, without question, but I don’t think they would have resumed their sexual relationship. Maybe they would have every once in a while—you never know with Mikael!—but after Lisbeth essentially got her heart broken by him, I don’t think she would have committed to a sexual relationship again.

I also think that the third book left them in good places with other people in their lives—Lisbeth apologizes to Miriam; Mikael starts a relationship with Monica (was that her name? it’s been some time since I’ve read the novels; I’m planning a reread before the remake comes out) and admits to Erika that he might be falling for her. Admittedly, I was a huge fan of Mikael and Erika’s relationship because it was such a unique dynamic! Erika had such a strong relationship with her husband, but she also loved and deeply cared for Mikael, and I don’t think they would ever truly be able to give each other up, not with all they’d been through.

Given the lengths that Lisbeth and Mikael had gone through for each other, I do think they would have remained close friends, although I imagine the trust would take a little longer to rebuild. I absolutely love the note the third book leaves them on, of Lisbeth finally letting Mikael back into her life. I don’t know if they’d ever get back to that romantic connection, but I don’t really think they need it—their connection is deeper than that.