As most of us have figured out by now, labels are more of a guideline than a hard rule, and quickly break down when the lines begin to blur.
I am a born male who identifies as transgender, wanting nothing more than to have a biological, genetic female body. But so far, despite that identity and wish, I am attracted exclusively to women. Does that mean if I transitioned I would be a lesbian? Does that mean, if I am actually a woman's brain inside a man's body, that I am already lesbian/gay for being attracted to women? It's kind of ridiculous if you tried to make it fit, but it's also kind of amusing. So I guess you could say I am still a straight man since I have not even started HRT yet. And I am attracted to trans women because they are women. The only time I have ever felt even remotely attracted to a man was when he was extremely feminine, as in some Japanese "Visual Kei" rock stars. It's funny how I, still in the closet, can openly discuss with another straight man how hot Japanese Visual Kei rock stars were, despite them being men, and it doesn't seem weird. So maybe it is a better logic to describe people as being attracted toward masculine or feminine rather than being attracted toward men or women. But even that wouldn't be a perfect solution, because I am sure there are people out there who are attracted to both masculine women and feminine women, but would be thoroughly uninterested in any kind of man, or any kind of trans, even after the surgery.
On a side note, I'm actually hoping that I can learn to be attracted to men after I complete my transition, as part of my transition. I really don't know where that hope comes from.