I think, based on reading what other serious thinkers who are in the LGBT community have posted on the subject, that the argument for "dropping the T" isn't based on the transgender community not needing support. It's more that the LGB part of the acronym is centered on same-sex attraction. The T is not, and in some cases actually conflicts with it. ("I'm not gay, I'm born in the wrong body.") They argue that there are trans activists who want to make gay people straight instead of accepting their homosexuality.

That said, your point is still a very valid one. And someone who is trans will have to deal with the same-sex attraction issue one way or the other (unless they claim to be completely uninterested in sex).

I don't have a dog in the fight or strong opinions either way, but there are decent arguments on both sides. My guess is that inertia will keep the T in the acronym.