No. According to the most recent study conducted in the U.K. with a sample size of about 800, the percentage of heterosexual transsexual females is approx 33%. Many of these Trans-women identified as homosexual males prior to transition. Another 1/3 identify as bisexual, and the remaining 1/3 identify as lesbian or asexual.
Prior to Transition, since they are functioning in a male role, a large number of Transsexual females attempt to have relationships with women (some very satisfying.) These appear to be typical heterosexual relationships. Once a Transwoman accepts her condition and begins to live her life as a female, things can get very confusing, especially if she had difficulty with the aforementioned heterosexual relationships. Things can get even more confusing if she is attractive and starts to receive attention from men. It's not unheard of for Transsexual women to find their sexuality seems to change in the course of Transition. What is actually happening is that the her true sexuality, which was repressed as part of her attempt to function in the male role, begins to emerge. Once she is free to live as a female, so too her sexuality is freed, and she can entertain relationships with males and not feel as though it is a homosexual relationship.
So to the outside observer, the Trans-woman's sexuality seemed to change, when in fact it simply came into alignment along with the body/mind congruence. Of course, not all Transwomen experience this. Some continue to pursue relationships with both genders, while others are never attracted to men and identify as lesbian after they Transition - all the more proof that gender and sexuality exist independently of each other.
It amazes me how such a simple concept is lost on so many people (Heather for example.)