You're talking about two different animals here, one has nothing to do with the other. As has been stated, Real ID is a federal requirement and will need to be implemented by each state. Exchanging one license for another has to do with the ability of a state to accept or deny the transferring license. Some states simply accept the credentials and issue a new license, some force you to take a written/road test. The big thing here is whether or not TN will accept a license without being RealID verified. I'm thinking no.
However, thinking about it, TN may just say you can transfer the license, if you provide proof for RealID at the time, and issue you a license. However, you will STILL need a new birth certificate if you don't have a passport.