That Star Trek was sexist in the 60's hardly makes it okay to be sexist today.
The scene could very well be somewhat meaningful in the movie, most likely it's supposed to make us laugh, but in the context of the trailer it's really strange. It's just a woman in underwear, totally unrelated to the rest of the trailer. She should not be there,
Sexy and Sexist are not the same thing. A character (male or female) can be smart, funny, and kick ass, and still be sexy. The amount of clothing does not make a character less or more sexist, it's the script and how the actor handles the scene. If Alice Eve plays Carol the way we know her: Unimpressed by Kirk and his "rep", willing to tell him off, self confident and wicked smart, then it doesn't matter what she's wearing.
It's jumping the gun a bit when ever a woman shows a little flesh in a movie (especially sci-fi) that automatically the assumption is "Oh noes, the sexist!!1!!"