It looks like Project Cars 2 is coming this year, and will be landing somewhere in fall 2017. Developer Slightly Mad Studios, keeping to their namesake is quoted saying that it will be coming "Septemberish".
A forum post reveals CEO Ian Bell addressing the racing sim's sequel release schedule. "It's still a very tight run as we're a bit behind on GUI and Career so nothing is set in stone yet. Current guess is Septemberish." He has also promised that none of the famous car brands will be missing. In the original Project Cars, some highlights were missing, such as Ferrari, Porsche, and Lamborghini, but that seems to not be the case with the sequel.
Project Cars 2 is being crowd funded and developed with the communities help, something that greatly helped make the first game as good as it was.