Transhumanism is the realization that exponential increase in technology yields a rapidly changing world; a world where everything is affected in some way by technology, and a world where control over technology is an awesome power.
One can easily conceive of a transhumanist fascism. Existing undesirables would be mentally and physically crippled to the extent that it made them useful slaves and nothing more. Due to the extent of slave labor, a much smaller ruling class could exist, populated by augmented Übermensch, and hyper-augmented rulers. This regime would likely be permanent, as there would be no way to ever break the control the dictator or oligarchy exerted on the rest of humanity.
Many transhumanists are laissez-faire capitalists, because most transhumanists are rich white men. As transhumanism becomes an obvious reality, rather than a fantastic hobby of rich white men, all political ideologies will be implicitly transhumanist.
There will be transhumanist liberalism, transhumanist neo-liberalism, transhumanist communism, transhumanist fascism, and transhumanist anarchism.