Yeah, it's possible that your orientation might "change". People that do experience a change typically experience an expansion in the people they're attracted to, rather than a shift in a different direction. That being said, some people have experienced a shift in orientation, rather than an expansion, but it's very uncommon. And even when it does happen, you don't magically fall out of love with your partner

Now, the caveats. It's not simply hormones. Hormones could play a part, but self perception, self confidence and shedding of denial are also things at play. So you almost certainly won't find your orientation shifts just because you start taking HRT.

My own personal experience? My orientation "shifted", but also, not really... I'd spent my life dating women, but my attraction to them was always different to other folk. On the other hand, I had never experienced attraction to men, nor do I really have any memories of moments of clear denial of attraction to men. So I don't know whether my own experience was one of coming out of denial, or genuine change.

I'm still mostly sexually attracted to men, but I can be romantically attracted to anyone, and honestly, I value romantic attraction far more than I value sexual attraction, so I have mostly still dated women since I transitioned. My one time dating a guy, I felt like I had stepped out of one closet in transitioning, only to step in to another one when my queerness became invisible to people.

My relationships with women aren't very sexual (they never have been), but they're very intimate (they always have been), and that part hasn't changed with my transition, but my own understanding of my personal experience has shifted.