Be honest guys, PC3 sold absolute peas. Nothing. There was never going to be another game in the franchise. The only news we got about the 4th installment was Sir Ludicrous Claims saying it would be the "best game evar".
SMS lied in the leadup to PC3 so much and it was one of the filthiest things I've ever seen in a racing game release. The game itself might have been OK but it's not interesting or significant enough to warrant any attention either, and it didn't get any besides the negative response.
and remember, that was all without EA's help. SMS made a very subpar game and ruined all the faith in their brand, then got eaten up by a larger publisher. If they stuck with the PC2 formula and PC3 was a success, maybe EA would have kept the lights on. But as far as I'm concerned SMS sealed their own fate.
Also if you guys want another Project CARS game go play AMS2, it's on the same engine but it's way better.