Gender identity and sexual identity are two very different, very unrelated, things. A transgendered man could be attracted to men, women or both. There isn't a connection.
As far as bisexuals wanting transsexuals, that would just depend on the person I guess. Although, the people that are attracted to transsexuals or intersexuals, as well as men and women, normally refer to themselves as pansexuals. I myself am not physically attracted to the idea, but who can say who we're going to fall in love with, right?