Here is my take on things.
Low Population Servers
Alpha
Beta
Gamma
Delta
Epsilon
Zeta
Those on the 6 Low population (Origin) servers above will be paired with 2 Destination Servers
Eta
Theta
So everyone on Beta,Gamma,Delta,Epsilon and Zeta can transfer to Eta, or Theta.
The number of Origin/Destination servers are probably different and will change as BW get a better idea of how things are progressing.
I made a diagram.
Transfers Diagram In Layman's Terms