It depends on their implementation of TBC. I strongly suspect they will have fresh TBC servers and let us copy our vanilla characters over to replicate the experience of the organic process of expansion release without taking away the classic servers many people enjoy.
This being the case I could have both.
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There's no reason to let people include gold in the transfer at all. Give everyone a staple of X gold and let the economy start with a clean slate. Also why would they allow copying of characters under max lvl?