Without public clarification of the main developer “Dan” since a long time, FSPassengers for P3D4 was not really expected anymore by lots of fans.
One of his forum moderator wrote a statement to explain that it was not possible due to the lack of information access to P3D by Lockheed Martin.
As an alternative, you can have a look at “Self-Loading Cargo”, “Passenger and Crew Experience” or the donationware “Intelligent Cabin Announcement V2”.