According to Paul "Locki" Wedgwood
"Following E3, Splash Damage and id spent weeks reviewing the status of Enemy Territory. 2006 has been a great year for us, with incredible response from the press and the community. It's also been a challenging year, as the team here has given extraordinary effort towards completing the game this year. Unfortunately, sometimes effort isn't all you need -- sometimes you just need more time. To ensure the quality we want, we've decided to push the release out of 2006 to allow for extended testing, feedback and game balancing."
more info here:http://pc.gamespy.com/pc/enemy-territory-quake-wars/717741p1.html