Eh, Project Cars just happend, has more than 24 cars on track and rain. Its not running at a stable 60FPS but 1st party games are usually better optimized, so why shouldn't FM6 be able to pull it off?
I expect them to pull it off with graphics comparable or even better than Project Cars.
Project Cars isn't stable 60fps, and isn't 1080p though. Not that I'm saying they can't pull it off, but Project Cars really didn't come anywhere close.