Sulu pretty much asked to be made Captain, even if it meant less screen time for him in TUC.
No he didn't. He did refuse to sign for ST II if Sulu was just piloting the ship and delivering "Aye sir" dialogue, so Harve Bennett promised to add a scene where Kirk tells Sulu about his promotion, to captain of USS Excelsior (long before
anyone knew the ship would featured in the next film). While that one scene didn't end up making the final cut, it did give a suggestion that future movies might
be more fulfilling.
For ST III, he was pleased to get the scene flipping the guard.
For ST IV, he was pleased to do the scene in the Huey, plus he was promised a scene with his great great grandfather (a child in 20th century San Francisco), a scene that didn't get filmed due to failing light and a stubborn child actor.
He didn't request
to be a captain in ST VI, but was pleasantly surprised when he read the script, and that the "Hikaru" first name (from "The Entropy Effect" novel that first highlighted Sulu's loftier career aspirations). The writers knew that the promotion would appeal to the actor as something more interesting to do than piloting the ship.