I think the slow down is temporary.
As soon as the world population regains their financial confidence and security, the same level of purchasing and use of cars will be back. Likewise, it will increase as before.

What I'd like to see is for the OPEC/Oil nations to cut oil production and cause the increase in oil prices again.

This I believe will have a better and longer resulting affect in decreasing the dependency on combustion vehicles and strengthen the global populace in refocusing and strengthening their minds on trying, developing, and using, alternative energy, and transportation.

What will happen to OPEC? Will they get richer? I don't think so, I believe that an act like this will be the nail that seals the coffin. Let's just see how smart and or really greedy they are.

Let's not forget, it was the rise in oil prices that started the dominos falling.

Also, it may steer China now into alternative fueled vehicles. China I forsee will be a big player in filling in the void left by the Big Three here in th US of A.

Americans use to pay $25,000 for a decent, reliable, and safe mid size car, and now the Chinese will be selling them (exporting) at half the cost with little competition. Cheap, less safe, less efficient. They'll cut corners to keep that price down, and I forsee droves of poor desperate Americans getting in line to buy one.

Don't forget the Chinese. The more established car companies have been training them on manufacturing vehicles for the past three decades. They have the technology and know how, but not the ideals and standards the more established car companies have.