Toyota’s top-selling hybrid sedan is headed for a redesign next year. The popular Prius four-door is expected to once again differentiate itself with unique styling and class-leading mileage.

Although our spy photo shows an evolutionary shape, it doesn’t represent the final design. It was one of three designs Toyota was considering, but we’ve heard the final decision went to a more conservatively styled Prius more along the lines of the Hybrid X shown in Geneva this year.

Toyota officials have said recently that they hope to bring down the cost premium of hybrids while continuing to improve their efficiency. With new less-hybrid-friendly EPA testing procedures, the 2009 Prius may not show huge gains in its stated fuel economy figures, but its real-world numbers should improve beyond the current 40-45mpg range.

What this means to you: If gas prices continue to climb, the 2009 Toyota Prius could be the hottest new car on the market next year.