^Saavik and David travelling space with Kirk, Spock and McCoy was as unlikely as Marvel Comics aquiring DC Comics, or vice versa (for one, Merrick Butterick didn't want to play David Marcus forever, for two, most likely Robin Curtis also didn't want to play Saavik forever, so that shoots down your whole idea right there.) Nobody at Paramount was ever going to not have the rest of the crew there for the movies, as cool and amazing as you or others like you wanted this to happen (and what you just mentioned is only going to happen with the Kelvinverse characters, in particular Chekov not coming back in a future movie due to the untimely passing of Anton Yelchin.)