I don't think Ai could ever go back after that. The feelings of being a woman and experiencing true intimacy were just too powerful for her. She knew she had found her true self, and there was no turning back now. As the hours passed, Ai continued to explore her new female body and identity, feeling more confident and comfortable with each passing moment.
And as for JC, well... he had proven himself to be quite the understanding friend and guide throughout this entire process. Perhaps their connection would continue to grow even stronger in the days ahead.