It's such a rare idea, to actually end a game franchise. Videogames come second only to comic books in their tendency to be perpetual – while movies, books, plays, albums and so forth are more often than not standalone (even in this day and age), and even TV shows are expected to eventually end, it’s exceedingly rare to see a video game created without any chance of a followup, and also very rare for a successful series of games to be deliberately brought to a permanent conclusion.