IIRC she was Heiress Apparent for a time, but due to outside pressures empress Wu was forced to appoint someone from the House of Li (the Tang dynasty) as heir. Let's say this doesn't happen, for whatever reason.This will make female emperors more than just a unique phenomenon, and moreover - it has the potential to dethrone completely the Tang dynasty and replace it with the Second Zhou Dynasty.
What further ramifications to Chinese history might this cause?
EDIT: It appears I am wrong and Taiping was never heiress to Wu.