Time Mage is AST, or at least served as it's basis (with a bit of Chemist thrown in as I recall).

Also, given SE are now adding entirelly new Jobs based on the abilities and signature weapons of individual FF characters from past games (GNB being based on Squall from FFVIII, VPR based on Zidane from FFIX etc), this is even less likely to ever occur, if ever. (Personally, I'd say to just rename AST as Time Mage and be done with it, but.... that's never going to happen either.).