I guess I am one of the lucky ones. I got a server merge very early. Maybe thats because I'm on an RP server and merging the three was not a big problem.
But if you consider the amount of population amongst the PvP and PvE servers that is spread about. I would say thats still quite alot. Filling destination servers would have to be trickled in as people agree and move. Once they are happy that the server is stable or full, then move onto the next destination server. And so on.
If they moved everyone at the same time, it would be chaos. Thoes unsubed at the moment, I would say have a time for a while before the mergers actually stop and the Dev Team move them to a server of thier choice of whats left I suppose.
Servers are not closing down as the mergers go on, so I guess thats to give the unsubers a chance to make thier decision.
Any way, I hope those who have not got thier destination server yet don't have to wait much longer. And I hope it improves things for you like it did for me. Good Luck