The basic theme is technology-driven change, with the pace of change in cars accelerating to match the worlds of non-traditional auto technologies (think video games, satellite radio and TV, MP3 players, hybrid battery systems, and embedded computer systems, to name a few).
A key trend is the diversification of the marketplace, with flexible manufacturing based on common vehicle "platforms" freeing up manufacturers and designers to build ever-more specialized niche-market vehicles. The Chevy Colbalt-based HHR is a case in point. (Rather than look at model sales as an indicator of automaker success, perhaps we should be looking at platform sales.)
It will be interesting to see related industries (independent automotive service and repair, for example) adapt to the pace of change and the proliferation of complex, technology-rich vehicles.