Post menopause. Will HRT make my new breasts grow again? (Photo)

That depends on how much of your remaining breast tissue is glandular. Usually breast tissue has fat and breast gland tissue. The gland element may respond to hormone therapy but my guess is not by very much. Your plastic surgeon may be able to give you a clue from the pathology report on your reduction breast tissue, as they can quantify what your percentage gland is likely to have been and probably still is.