From what little I understand based on my reading of Max Heindel (mostly the Rosicrucian lectures) and from personal knowledge, gender goes away -- or it becomes something we cannot understand -- when we reach the causal plane. The causal is one level more subtle than the mental plane, and the mental is one level more subtle than the astral plane. As far as my own self, I was female my last spin and male before that a couple of times.