It wont happen properly with true realism for a good generation or two I doubt, with the amount of calculations you need to actually have a realistic crash, you'd have to have fully modelled chassis to quite a silly detail to get correct deformation etc, it'd take ages to render a few frames on a normal PC/console I'd have thought.
How much fun it'd be in a proper race game, I don't know. It'd probably be great for the ultra-sim nuts out there, but for those that want a little effortless fun, then they don't want their cars to rip to pieces every time they make a little mistake.