RollerCoaster Tycoon World

Rollercoaster Tycoon 4 will be the 4th game in the Rollercoaster Tycoon Series

History
While the game hasn't been officially announced, "A message to our RCT faithfuls 8/14" appeared on the Atari Forums on 14th August 2010 indicating that Atari is contemplating the series' next installment.