In the USA the courts have decided that transgender folk can use the toilet for the gender they identify with. To save me from discussing whether we need some kind of ID card that states our gender identity, we can just take it to the next logical step – wouldn’t that discriminate against those who are gender fluid or non-binary?
If gender fluid folk can therefore use any toilet they choose, then people with ill intent can just wander into toilet they want, and claim to be gender fluid. That’s where we will end up.
Aside from different functional needs (tampon disposal, urinals), and potential embarrassments, there’s another strong reason why most toilets are segregated. Many women do not feel safe going into a private area where strange men might be. Possibly most women.
So here’s my prediction. Rather than a toilet entrance that leads to booths, all booths will be directly accessible. Each booth will have its own internal hand basin and mirror, so they’ll be a bit bigger. A separate urinal room will be for people with penises only. It’ll be more like portaloos at an outdoor festival, and less like the office toilets we know today.