I considered making a prediction at Long Bets and may still when I can scrounge up the $50.
My prediction is that it will be possible to buy a car or other human transporter without a powerplant, leaving the choice to the buyer (electric/hybrid/internal combustion [gasoline, diesel, biodiesel, methane, hydrogen]). The underlying premise is that the drivetrain fittings will become standardized like radios and CD players. The form factor of the different types of cars now — everyday I see hybrids, biodiesels etc. — so it makes sense for manufacturers to disintermediate themselves, offering styling and comfort level with your choice of powerplant.
I figure 25 years before this is an option, and it need not be a mass-market option: it could be some clever small manufacturer who wants to leverage value(s) instead of pure market efficiency, ie, cost. I think this could lead to some innovations in the body and passenger compartments as well as people specialize in those.