Sure, we've already answered this one at the Guild Summit: At present time, we will not be offering the ability to change the race of your existing character.
Dear George. If you're going to answer a question from the Q/A please answer the entirety of it. Especially this one which is weighing heavy on ANY PLAYERS MIND that has leveled alts while waiting for 1.2 (instead of quitting the game.)
Ziko: Already having 8 characters on my server...will I be forced to delete characters in order to take advantage of the Legacy system or will I be able to change race & new Legacy customization features on pre-existing characters and will there be more character slots added?
Georg Zoeller (Principal Lead Combat Designer): We have heard at the Guild Summit that there's interest in being able to acquire additional character slots on the servers. We are in the process of determining the requirements for such a step and will update the community when such a feature has moved past the planning state.
Please answer the first part of the question that is entirely more important than adding additional slots which you don't even know if you're going to do or not.
There are plenty of us that do not want to have to delete our characters that we got to 50 because your character options/customization was so limited to begin with. (If you say it's not limited, I'd suggest going back to how many threads were on the beta forums about Character creation.)
As for applying unlocked legacy customization features for character creation to existing characters, please see Damion's answer regarding the 'Barbershop' feature.