Don't take it on. It's possible to think that you'll be able to WOW Classic TBC Gold continue playing your character in Classic, but you won't. This is particularly applicable if you've cleared Naxxramas. If you want to continue playing Vanilla, just start over with a different character, it's going to be much more fun and fulfilling

People who want to complete maximum but don't have the resources to achieve it at present, either with modifications to tbc or staying in the classic. They can find new guilds, and start raiding nax completely from scratch , starting a brand new raid. They'll have to buy the cloning services if they plan to play in tbc. Because the original WoW community is no longer in existence and the cloning service is no longer available, it should be completely free.

All servers currently running will be TBC servers. Start new Vanilla versions of these servers. You have the option of activating the character on the TBC server or the Vanilla version. You'll have to pay to activate the same character on both.

Edit: Blizz's own article on it. "On Patch day, players will be able to launch the Battle.net desktop app and select which game you'd like play: Burning Crusade Classic, or WoW Classic. Your current characters will appear in both games under your old name/s. Once you've chosen one of the games to play you'll select a character to play, and confirm your selection. If you decide that you'd like to play with your character in both game types, you'll be able to make use of an optional service for access to the cloned version of your character in both games. All you have to do is log in the game as usual and begin playing.

Because the copy is complete before release Yes. All characters are present in Classic There is no downtime for copying if you choose Classic. If you choose TBC the copy might result in downtime (just because its not instantaneous) and imagine a number of people's characters being copied at buy TBC Classic Gold the same time which could slow the system down.