Still less than 1% of the population, and that number could dwindle if and when treatment sorts out the underlying problems with the mental wiring causing the gender dysmorphia, and the current trend dies out.
Trans people have been around forever, and aren't going away just to make image classification less complex. It's not a "trend", treatment options just happen to be more available and the internet makes communities more visible now.
So the solution would be to not identify _anyone_ as people? As a ginger I doubt that.
https://adssettings.google.com/u/0/authenticated
Here Google can infer my gender and my age and personal interests just from my search history. I am sure this is not perfect either, it is still immensely useful for advertising.