For some years Michael Sivak, of the University of Michigan, has been monitoring vehicle ownership and distance driven in the US. His latest report shows that light duty vehicle ownership per person and per household both peaked in 2006, and that distance driven per person and per household reached their maxima in 2004. (Light duty vehicles are cars plus trucks with two axles and four tires.)
There has been some revival of distance driven per capita in recent years, but I would not expect any long term growth above the present plateau, given both time constraints on personal travel and speed constraints on the road network.