From what I recall, Sulu was always still slated to take command of the new USS Excelsior
after the return of the cadet-training mission (per the Wrath of Khan
novelization), but it was only mentioned that his old friend and former shipmate (Capt. Mandala Flynn) had been given command of one of the Galaxy
-class starships on a mission to the Andromeda Galaxy.
(How times change...)