I really don't want to be simply another contributor to further derailing this thread, but I feel the need to step in with a voice of moderation.
I don't think anyone can honestly expect cars to be completely unnecessary in the future, particularly in rural areas. Â It's just as wrong to assume that cars are inherently bad as it is to assume they are the only practical and viable option for human transport. Â Our transportation problems due not exist because cars exist, but simply because we have become excessively dependent on them. Â Personal automobiles, trucks, and motorcycles are a perfect for far-flung rural populations and as new technologies such as hybrid and electric (I'm not so optimistic regarding the fuel-cell and hydrogen pipe-dreams) power systems develop, they will continue to be a practical and efficient solution.
The fact is, however, that only about 20% of the US population lives in rural areas:
http://www.fhwa.dot.gov/planning/census/cps2k.htm . Â This leaves the other 80% of us in the position to have a balanced inventory of transportation solutions, where mass transit can be more efficient and sustainable.
Personally, I feel that the two main reasons we are so dependent on cars, even in urbanized areas: 1) we have become so accustomed to to personal cars that it is difficult to imagine another options, and 2) our short-sighted next-election focused political systems favors auto transport and highways because it does not require the degree of long-term planning and community effort that mass transit does. Â We hardly keep up with the traffic congestion on current highway projects, yet countries like China are planning rail systems that will efficiently serve the population for the next 75 years.