Terminator 4 is expected for release in either 2009 or 2010. According to an interview on February 1, 2005, Nick Stahl and Claire Danes will not be returning for Terminator 4.

On May 9, 2007, it was announced that rights to The Terminator series had passed hands from producers Andrew G. Vajna and Mario Kassar to the Halcyon Co., a privately funded company formed by entrepreneurs Victor Kubicek and Derek Anderson.

In the Variety article detailing the purchase, it states the fourth film is now earmarked for a Summer 2009 release and will focus on a 30-year old John Connor in what the producers hope will be a new trilogy. Series creator James Cameron and star Arnold Schwarzenegger are currently not involved with the project.[1]

On May 29, 2007 Comingsoon.net revealed model/actor Marcus Schenkenberg has signed on for Terminator 4. It also mentions that Governor Arnold Schwarzenegger will have a 30 second cameo. It has been confirmed that T4 will take place after the events of T3, and will focus mainly on the war between man and Skynet.

On July 19, 2007, the film news site Dark Horizons revealed that the Terminator 4 project is currently in legal limbo due to a lawsuit between MGM and Halcyon subsidiary T Asset.[2]. According to the article, MGM has an exclusive window of 30 days to negotiate for distribution of the Terminator films. When negotiating for Terminator 4, Halcyon rejected their initial proposal, and MGM suspended negotiations. After the 30 days was over, MGM claimed that the period during which negotiations were suspended did not count and their exclusive period is still open. Halcyon is now asking a court for an injunction allowing them to approach other distributors.

Taken from: http://en.wikipedia.org/wiki/Terminator_4