I'm not really sure what the future of Trek would be like for Trans people. I have no doubt that there'd be no transphobia, and that really excellent, even perfect gender reassignment would be easily available. Beyond that, I'm not sure how that would be implemented. They could easlily make a passing reference to one of the characters having been born the biological opposite gender and had gender reassignment, but the Federation should be progressive enough that there'd be no struggles based around it.
I totally support having a trans character, but unless an actual trans actor plays the part I don't see it making much impact.
I totally support having a trans character, but unless an actual trans actor plays the part I don't see it making much impact.