But that would be odd, considering most of PR's senior officials right now are NPP and Republican.
Yes, because the main fault line in PR politics today is, whether to become a state or not: NPP is for statehood and PDP is for the Commonwealth. However, once that fault line is removed, national politics would take precedence, at least in federal elections. True, at present it appears that Republicans are dominant in the NPP. This is why I am saying that it will only a minority of NPP will go into Puerto Rico Democratic Party. Nevertheless, it's going to be a large minority - and, given that PDP will merge into the Dem party wholesale, this will be the dominant party in PR.
I could imagine that NPP and PDP would, actually, retain their identities for the state-level elections . But in Federal races the national two-party logic will impose itself.