As we all know, invent the most efficient hybrid car and we will soon find something else(non hybrid) that gets better fuel mileage. It is this iterative process and the competitive challenge that creates advancements. Look at all the recent innovations in magnet and battery technology that are the result of competition. We are nowhere near the routine production of hybrid cars. There are many theories as to how they should be done and continuing advancements that will change those theories. With the increasing price of fuel, I would suspect that we will see more and more innovations over the next few years.