Warner Bros. has given up the rights to the Friday the 13th franchise along with certain rights to South Park in order to snag Christopher Nolan's upcoming film Interstellar. The studio made the move to gain most of the profit and promotion from Paramount Pictures, the studio currently making the film with Nolan. This now means a future Friday the 13th film and a portion of a future South Park film will be co-financed by the two studios. It also includes that Paramount will co-finance an unannounced future Warner Bros. project. My guess is the project will either be Justice League or a new Batman movie.
Now... let's be clear that future South Park and Friday the 13th films are not currently in production or real planning stages. Warner Bros. put Jason Vorhees on the back burner due to the fact that PG-13 horror movies are kind of popular right now so they don't want to rock the boat with an R-rated horror release. It also has something to do with the fact that Paramount had some sort of property claim on both of these as well. Now that they are back to Paramount new movies for both are pretty likely to be pushed forward.