In breaking with the previous three movies in the franchise, all rated R, Terminator 4 is shooting for a PG-13 rating. The new rating goal isn’t entirely surprising, given that the successful Terminator: The Sarah Connor Chronicles has widened the fanbase on Fox with a TV series that probably would rate PG-13 on the film scale.
The fourth Terminator movie is titles Terminator Salvation: The Future Begins and stars Christian Bale as John Connor. It currently is slated for a May 22, 2009, release.
Source: Sci Fi Wire