Gnome 3 is the first major release of the open source project since 2002. The rumors about Gnome 3 started in early 2008. The plan was to avoid major user-visible changes, and limit the update to cleaning up the code. After a while they noticed the interface could use a touch-up as well. Here's what the Gnome Release Team has to say about it:

"GNOME releases every six months to provide a reliable platform for its community and downstream partners. While it might be possible to release GNOME 3.0 in 2010 by slipping the schedule by a month or two, it makes more sense to stick to GNOME's release schedule and ensure that GNOME 3.0 lives up to the quality that our community expects." [source]

This terrible news was announced at the Guadec conference last week, which is held in the Netherlands. The comforting news is that september won't be completely useless, and will provide us with Gnome 2.32. A new preview release of Gnome 3 will shipped as well.