No specific reason for the change is given, but the team behind RCTW says they are "excited to continue working on RCTW, and are 100 percent focused on creating the next great RCT game!"
RCTW will feature the same blend of park management and rollercoaster design that the series is famous for (we'll still hopefully be able to blow of steam by creating elaborate deathtraps for unsuspecting guests), but also adds the ability to form a theme park corporation with friends to compete with others worldwide.
"Specializing in online PC gaming experiences," reads an announcement on the game's website, "the Area 52 Games studio has brought together a team of veterans who have worked on major IPs across simulation and strategy genres, including Tropico, the Sims series, the Railroad Tycoon series, the original Pirates, Age of Empires, Forza and other well-known games. Many thanks to Pipeworks for all their efforts in getting us to this point in the development of the game."
RollerCoaster Tycoon World is still planned for release in "early 2015".