I believe you need to define FUTURE. If you are talking 25 years, I believe we will still be depending on gasoline to power cars. However, I believe alternate fuels such as bio-diesel, methanol, and batteries will become more prominent.
If you are talking 50 years, I believe the car as a personal mover in some form will still be around, but I don’t believe it will be powered by anything like we have today. I believe that car will rely on some sort of electric motor. By thie time, I also believe that we will have likely diminished our commuting needs. We will have less need to commute to work centers because for many of us, our work will enable us to telework either from home or from remote telework centers. I expect that cold fusion will be developed by then, to the point of being able to provide direct power or to use in extracting hydrogen from sea water, for use in powering some sort or battery for these personal cars and other power needs.
Beyone 50 years, we will be using power generating technology that is not even in our vocublary yet.