When you used up your best idea to extend the franchise two movies ago and need something to grab people's attention it's time to threaten the world with ending a series! Be it by saying the main character might die, or by simply (blog) doing what Paramount did and claiming the series would (blog post) be ending while at the same time continuing to plan for sequels.
Source: Friday the 13th: The Final Chapter Movie Review - Decker Shado