Here's what happened to Dr. Leonard "Bones" McCoy after Star Trek: The Original Series and the six movies that starred the classic crew of the Starship Enterprise. From 1966 until 1991, the late DeForrest Kelley portrayed the gruff but loveable Dr. McCoy, whom Captain James T. Kirk (William Shatner) affectionately referred to as "Bones". However, McCoy's remarkable Starfleet career lasted well into the 24th century, long after Kirk and his original crew embarked on their final mission together in Star Trek VI: The Undiscovered Country.
For 27 years, Dr. McCoy served as the Chief Medical Officer aboard the U.S.S. Enterprise and Enterprise-A. Bones was a key player in Kirk's original five-year mission, forming a triumvirate with his best friends Captain Kirk and Mr. Spock. McCoy retired from Starfleet after the five-year mission was completed but he was drafted back into service using a little-known 'reactivation clause', just in time for Kirk to command the Enterprise against V'Ger in Star Trek: The Motion Picture. Bones resumed his post as Chief Medical Officer and became the host of Spock's katra (his soul) after the Vulcan's death in Star Trek II: The Wrath of Khan until Spock's resurrection in Star Trek III: The Search For Spock. In Star Trek VI, Bones and Kirk were wrongly convinced of the assassination of Klingon High Chancellor Gorkon (David Warner) and were imprisoned on the penal planet Rura Penthe. After Spock liberated them, Bones helped the Enterprise crew uncover a conspiracy and successfully fostered peace with the Klingons.
Surprisingly, Bones remained in Starfleet after his service aboard the Enterprise was over, although McCoy didn't join Captain Kirk on the maiden voyage of the U.S.S. Enterprise-B when Kirk was presumed killed by the Nexus in 2293. However, an elderly McCoy made a cameo in "Encounter at Farpoint", the pilot episode of Star Trek: The Next Generation. In 2364, after the U.S.S. Enterprise-D commanded by Captain Jean-Luc Picard (Patrick Stewart) arrived at Farpoint Station, Admiral McCoy was accompanied off the ship by Lt. Commander Data (Brent Spiner). Bones was aboard inspecting the medical facilities of the new Galaxy-class starship and when Data correctly stated that the Admiral was 137 years old, McCoy checked to see if the android had pointy ears like a certain Vulcan he once knew.
DeForrest Kelley's Bones was the first of five Star Trek TOS characters to meet the crew of Star Trek: The Next Generation; Sarek (Mark Lenard)), Spock (Leonard Nimoy), and Scotty (James Doohan) would all appear on the series while Kirk met Picard (and died) in the Star Trek Generations movie. While "Encounter at Farpoint" was the lone appearance by McCoy in the 24th-century era, the legendary Doctor would be mentioned in the other Star Trek series.
In the Star Trek: Deep Space Nine season 5 episode "Trials and Tribble-ations", Captain Benjamin Sisko (Avery Brooks) and his crew time-traveled to the 23rd century and met the crew of the Starship Enterprise, including Bones. Lieutenant Jadzia Dax (Terry Farrell) confessed that Emony Dax met Leonard McCoy on Earth in the mid-2240s. Emony and McCoy apparently had a brief fling because Jadzia recalled Emony's memories that "he had the hands of a surgeon". In the Star Trek: Voyager season 2 episode "Lifesigns", The Doctor (Robert Picardo) mentioned that in 2253, Dr. McCoy created a surgical procedure for the humanoid brain that involved grafting neural tissue to the cerebral cortex, which notes how much Bones has positively impacted medicine in the 24th century. McCoy's templates are part of the design of the Emergency Medical Holographic doctors used aboard 24th-century Starfleet ships, which includes Bones' favorite catchphrase, "I'm a doctor, not a ____!"
Star Trek TV and movies have not canonically stated if and when Leonard McCoy died. In William Shatner's non-canon Star Trek novels published in the 1990s, Bones is alive in 2379 thanks to cloned and artificial body parts. Also, the IDW comic book Star Trek Special: Flesh and Stone depicts an ancient McCoy using a wheelchair similar to Captain Christopher Pike's as he lives at the Viirre-5 Agricultural Cultivation Facility. Though he would be roughly 172 years old, it's even possible that Bones could still be alive during the era of Star Trek: Picard.