Vaporware, n. /vay'pr-weir/ (UK "vapourware")
Vaporware is a term reserved for products announced far in advance of any release date (which may or may not actually take place). The term came from Atari users and was later applied by Infoworld to Microsoft's continuous lying about Microsoft Windows.
A contemporary example of Vaporware used to be the title Duke Nukem Forever, which was announced many years ago, and for the longest time, it seemed like it may never be released. It was eventually released in 2011 to much criticism.
A more recent example is the video game Star Citizen.