We caught a glimpse of the next-generation Sky-G (gas) and Sky-D (diesel) powertrains when Mazda presented them at the 2009 Tokyo Motor Show. Presented at the same time was the new Sky-Drive six-speed automatic transmission (do you sense the sky theme yet?). These engines are currently being tested, as they are expected to show up next year in the refreshed Mazda6 sedan.
An early test by Car and Drive showed that the 2.0-liter Sky-G engine can achieve 30 miles per gallon in the city and 39 to 40 mph on the highway. This has it competing against the VW Gold and Jetta TDIs, not to mention beating smaller offerings like the Ford Fiesta and Honda Fit. The Sky-D diesel powertain will achieve up to 43 mph on the highway, and may be used in the next-generation mid-size sedan (maybe the Mazda6?).