I believe that they should just have 1 server if it can handle around 8k people. if they cant, release 2 or 3 realms and then merge since the timelines would be the same (ie: zethkur). open it up when available to all servers. let anybody transfer to it as vanilla gear really doesnt matter anyway as by the time you hit 63 blues and greens are better than naxx gear. since it just a copy people can still raid on vanilla and lvl in TBC. Guaranteed most people will leave Elysium server and start fresh on TBC anyway. Fresh servers will always get the pop.