I think it's complicated, like other people said. Since our model of sexuality is about your own gender in relation to the gender or genders you're attracted to, coming into your own identity can make all of that complicated.
I identified as a lesbian for a while, before I had words for being trans*. I knew I wasn't solely attracted to women even then, but the idea of being a woman in a heterosexual relationship made my stomach sink. After coming into my identity as a trans man, I identified as queer and toyed with pansexual.
I've been on T for a couple months now, and I've been identifying as a trans fag also. So I guess I'm attracted to people of all genders, its always been that way-- I've just always had an aversion to straight people haha