All our characters exist in WOW TBC Gold Classic already. They definitely don't want to waste time for anyone who is planning to TBC. All characters will be copied before launch. TBC will change the "active bit" on the TBC database to true and the Classic bit to false when you choose TBC. Then , you pay them $35 to flip that Classic bit back.
Ion discussed retail WoW. There are no servers, however, there is a massive server that lets you play with any player within your region. The cheap Burning Crusade Classic Gold game is balanced, though Alliance tends to have more skilled players than Horde.