@dalias it'd sort of be like when aspergers syndrome got re-classified as autism spectrum or "high functioning autism". i know a lot of aspies were disappointed and still call themselves aspies.
culture however is another matter entirely, and of course there would still be gender at the cultural level. it's pretty deeply ingrained in all of us. gender as a cultural concept is pretty much not set in stone though.
for example in thailand, there is the "third gender": https://en.wikipedia.org/wiki/Kathoey