Why even give the players an option of a server move, just move them to another server and have done with it.
what is going to happen to the people on the server now otehrs have moved, going to be even less people than before. Personaly, and i did do this as it happened to me, i had a few chars on other servers and founf people lacking. So i just bit the bullet and found a server where people where on, some OCuK too and re-rolled there. left behind a few lvl 15+ chars, but at least now i have people i can have fun with.
If i was in charge, id email all the users on the bottom 25% pop servers and let them know that in 2 weekends time, all users from your server are going to be moved to the new server, free of charge. would have liked to have seen you move to 8peaks server V3g3tto, but hey, cant have everything now can we )