UPDATED 7/8: See below.
Actor John Cho, who plays the character of Hikaru Sulu, the helmsman of the U.S.S. Enterprise in the rebooted Star Trek movie franchise (which has been officially dubbed the “Kelvin Timeline”), revealed while on a promotional tour in Australia that his character will be revealed to be gay in an upcoming scene in Star Trek Beyond. The revalation will be muted – “I liked the approach, which was not to make a big thing out it, which is where I hope we are going as a species — to not politicize one’s personal orientations,” according to Cho.
However, in an interview with THR, the original Sulu George Takei says he is unhappy with the decision to take an established character rather than present a new character. When Cho called him to tell him the news, “I told him, ‘Be imaginative and create a character who has a history of being gay, rather than Sulu, who had been straight all this time, suddenly being revealed as being closeted.'”
Takei, who came out of the closet in 2005 and has since become a vocal supporter of LGBT rights, had a discussion with director Justin Lin, and believed that they had rethought the decision. But when Cho had emailed him about the promotional tour and that the revelation would likely come out, Takei was disappointed.
The character of Sulu as originally depicted appeared straight although it never was formally established outside of secondary sources like novels. What was established is that he had a daughter, Demora Sulu, but whether she was adopted or not isn’t necessarily canon. However, given his occasional targeting of women including Uhura, if he was actually gay that would seem to indicate that he was “in the closet” during the original mission – which would raise the question as to whether there was a closet in the 23rd century to be in.
Update 7/8: Simon Pegg gave a very reasonable counter-argument.