I think it'll pull through. From RPF fandoms I have seen, they rarely die down when people get official partners. Generally, in the better ones, it's a lot of pretending the partners away for fic purposes, a certain degree of open-relationship fic (which, if it's a happy open relationship, doesn't squick me, personally), and a few angsty breaking-up-the-real-couple fic (which does squick me).

In the worse ones - well, we've all seen Supernatural fandom.