The Harmon Hotel is the one part of CityCenter that hasn't opened. Construction flaws caused the building to be capped at half the original size. Now the building is locked up in courts to determine if it is safe to complete, and who's to blame.
MGM has been pretty quiet about the Harmon, but in their latest earnings release they concluded that "It is unlikely the Harmon will be completed using the building as it now stands."
While nothing will be done anytime soon because of pending litigation and MGM's financial woes, it looks like the Harmon will eventually be knocked down and the space will be used for something more appealing.