I really would not worry about appearing disloyal. If you don't take responsibility for your own career then who else will? In my experience there are some HT's who make a habit of dropping hints to their most capable staff about promoted posts that never materialise. I don't think you need to make excuses for the rather feeble "could be in the next few years" comment. If there really had been a position that vanished for reasons outside her control she could/should have shared the details with you. The nature of her reply does make me wonder if any such post existed - except perhaps on the HT's wish list. Good luck with your application. .