I thought that SJG was going to be putting together an epic Car Wars Kickstarter a la Ogre sometime in the near future.
As anarchy noted, Car Wars Classic is headed into distribution and Mini Car Wars is already available (maybe a Warehouse23 exclusive). These are both basically straight reprints of the 20+-year-old versions. I think Phil Reed said that Classic is a reprint of the 1990 edition.
The sixth edition (for Kickstarter) is still under development. A couple months back SJG brought back Scott Haring into a new Car Wars Line Editor position, and they are doing in-office playtests. Apparently driving and crashing is working adequately, so current focus is on rebalancing the shooting. I'd be surprised if it heads for Kickstarter before mid-2015 at this point.
[disclosure: although I'm a moderator for the Ogre forum over at SJG, I'm not an employee or directly involved in the Car Wars side.]