Does anyone know if the TRD Sport center exit exhaust is going to be just for the new RS, or will it be replacing the current TRD axle-back??

Fairly certain the center exhaust is just for the RS7.

and it sounds just like stock exhaust checked one out at the dealership

All Xb2 axle-backs sound stock unless the scuba is replaced... My TRD axle-back didn't change the sound at all so I replaced the scuba.