I've been mulling over how their relationship will unfold over the final 3 books. It's too early for a happy ending, but equally I don't think JKR will be so mean as to do anything really horrible for either of them.
Robin has to mature into being able to identify that it's unfair stringing on a boyfriend who she doesn't love as much as she loves her business partner. At the moment, I think she's so wrapped up in her trauma, and identifying with her past relationship with Matthew where he was the unreasonable one, that she can't see the wood from the trees. I don't know if we'll see Ryan being a PITA if she finishes with him or not, although it is likely.
I think the biggest spanner in the works will be that once they're in love and Strike has allowed himself to love her, then Strike won't be able to cope with her doing the jobs where she has to put herself in danger anymore. He already struggles with it, and I think it would be worse if she were his actual girlfriend. Like I said before, I also think that Robin may be in for some sort of mental health crisis having lived for months in such a state of high anxiety and starvation.
I think the end solution will be that they're together, and they have the agency, but they have to compromise on the field work, Robin will eventually get to this position herself I think. Or she'll explore work elsewhere in corporate investigation or something. I think they will grow together as romantic partners and their business partnership will cease to be as important to them.
Who knows if there are going to be unwanted pregnancies in the mix (Bijoux or Ryan), I think Robin being pg with Ryan's child is more likely and I think JKR would handle the storyline amazingly from a pro-choice perspective, whatever choice Robin made.