My guess is after the sale is over (the sale has been stated as being over on Feb 7th). That also fits with when they are releasing BWL on SoM (Feb 10th). I think they want as much money from the sale first as possible (people on even the lowest pop servers will freak out that they’ll miss out on saving $7.50 even for their alts, that’s how sales work).
I have a better suggestion to the server issue. Blizzard should reverse all transfers of those that left a dead server over the past year and move them back to that server give them there money back that they used to transfer and then make the cool down for those people to transfer again 1 year.