I'd identify as "oh fuck I have bad gender dysphoria again I wasted thousands of dollars on surgery and meds fucking monkey's paw did me rong"

Would my brain's sex characteristics switch too? Would my "female brain" become male along with my genitals? Since that's the likely source of my dysphoria, the question to that answer is also the answer to your question.

As an enby, I would still identify as an enby lol

Is this retroactive or do I remember how it used to be?

If it was retroactive I don't know. That's a lot of different life experiences and socialization.

If I remember how it used to be, I probably wouldn't care that much about my own body changing, but would have to grapple with not being attracted to most new-women-bodies.

I think it depends on the nature of what makes us trans.

I have body dysphoria for all the masculine attributes I was cursed with, I prefer the curves and soft traits common to women and preferred by societal norms. If men naturally had the body I want, now, but with the same behavior, societal status, etc, maybe I would be cis, just a little queer, a little effeminate in demeanor.

But since gender is more than just the body, I think, and with all other things the same besides sex traits, I'd almost definitely still be trans. So maybe I would still want to be a woman despite their harder, more angular bodies in this scenario. Those features would be what we consider feminine, and the whole package, rather than one part, is probably the likelier thing to want, psychologically, as a trans person.

Maybe I'd still prefer soft, smooth aesthetics despite the swap, so I'd have a masculine body (soft, smooth), but still identify as female, and with my current effeminate demeanor, instead of being cis. Or maybe I'd want to go through phalloplasty and take my estrogen to become big and bear-ish and enjoy my womanly beard finally growing in, because those things would be viewed as feminine, and I really just want the entire femme package.

Hell if I know! Fun thought experiment.

I think it would still be the case that I wouldn’t really feel a need to identify as anything in particular. It doesn’t bother me for people to categorize me as what they wish and I don’t think that would change. Some aspects of my personality would remain incongruous with stereotypes associated with my assigned gender, and others would match, just like they do now.

I mean my identity wouldn't change, people would just call it something different since it's no longer one of the default binary options