Well nothing in any series has said eaither way, the novels indicate he continued to serve as captain and had a long and distinguished career. In the novels, he was still the captain. There were other captains after him. William George commanded the Enterprise for five years during a deep space exploration mission in the Gourami Sector, mapped 142 systems, and made 17 first contacts. John Harriman became captain in 2398 and remained in command until after he participated in the Tomed Incident. Demora Sulu and Thomas Johnson Jr. each became captain of the Enterprise later on.