The awkward thing for Bath is that, if he doesn't make the RWC squad (which I think is a fair assumption) is that he has a get out clause at the end of each Union season, and the Rabbitohs made them include a clause that says if he leaves then they get first offer on him (for no "transfer fee").
If he loses out in the RWC, and isn't 100% enjoying his rugby in the rain and mud of Bath, then I imagine a plane ticket back to Sydney, to his brothers, will be mighty tempting.
Obviously this is a worst case scenario, and will most likely not happen.