If its a cutscene wouldn't
_cam cameraeffect ["terminate", "back"]
camdestroy _cam
suffice as once the camera is gone, the control returns to the player.
If its an intro, just end it. Like when a unit reaches a certain place just have a trigger activated by it and make it end1 and then the mission will start with the briefing.
Same with an outro except the whole mission will end.