I would guess with the lower population of Ran and Jin, that PWi is enticing all players to move to Isen so they can justify closing the older servers. If Isen's population goes up and Ran/Jin population drops to the point where is isn't feasible to run them, I can see them closing.
Then again, PWi could be using Isen as a beta testing ground to try out new things before adding them to the older servers. Could work either way.