Wouldn't be surprised to see more ex-MEX but doubtful on GRU.
RDU - MEX for example would make some sense (on either DL or AM metal). They run seasonally to the resorts but nothing to MEX though my guess is most DL traffic to SA from RDU is going through ATL already so may not make sense unless there is O&D -- presumably it would be at the edge of the CR9 range or the A220 if we see that come through RDU.