I'm not going to guess but I just wanna say that Dialga coming before Palkia doesn't seem likely to me. I don't think Niantic has ever released an good counter for a trio.
What I mean by this is that Dialga is the perfect counter for Palkia. It's steel typing negates it's dragon weakness. Palkia being water/dragon means that it's only weak to fairy and dragon. But fairy doesn't have a fast move yet and of course dragons are weak to each other.