Sony and some other companies will have receivers that can hook up in your car to your existing radio. The best part about it, is the fact it can be removed from your car and then used with your home stereo. Don't ask me how, I happened to read about it in an audio/visual magazine. I say start buying stocks in that company, I think that will be a profitable buisness.
I do beleive there will also be some sort of "Dolby Digital" six channel music available. If that happens that will revolutionize the way we listen to music in our cars. Ahh I can't wait to see what they'll come up with next.