1) Your question is a hypothetical that can never, ever happen, so no point in answering.
2) No one is born in the wrong body. There is no such thing as a female brain in a male body. There are men with dysphoria, as well as plenty of men with fetishes who want to live as women, but they don't have women's brains.
3) Despite number two, it is still not women's responsibility to move over and caretake for these men and their issues. I wish them well, but it's not my daughters' responsibility to shut up, sit down, and play nice with males who don't belong on their sports' teams.