AST is for sure getting CNJ because they mentioned cross classing protect in the live letter.
as for the second cross class i actually see it being arcanist, a healer without swiftcast, that would allow it to cross into both the healer classes, as the DRK is doing with both tank classes.

as for MCH, its probably going to be archer and lancer, archer because, well its the only other range physical dps class, and assuming MCH uses dex then it will also be the only class capable of making use out of hawks eye as a cross class.
Lancer because invigorate is just to strong to use anything else, and i don't foresee SE giving MCH their own version of it, of course i could be wrong.