They’ll obviously give people the chance to continue to TBC or stay behind in classic. They’re never going to deny us the ability to keep playing our characters into TBC. It would cause many people to quit entirely if we couldn’t play our current characters in Outland.
Most likely those who want to remain in classic will get the option to transfer to another realm or they’ll let those who want to move to TBC transfer. Classic is eventually going to die. No one wants to do Naxx forever. That’s why private realms would relaunch new realms and shit to start the journey anew.