While Audi readies its first hybrid model for launch later this year with the new Q5 Hybrid, rivals Mercedes-Benz and BMW are already working on their third and fourth gasoline-electric models.

Take Mercedes-Benz, for example. The automaker has already launched the S400 Hybrid and ML450 Hybrid, and now an insider has revealed plans for hybrid versions of the C- and E-Class sedans and also confirmed the existence of a production version of the Vision S500 Plug-In Hybrid concept vehicle.

Speaking with Automotive News, the insider said C- and E-Class hybrids would be launched in Europe before 2013 and the S-class plug-in hybrid, based on the next-generation S-Class model, would arrive in 2014. A second source said U.S. versions will follow about six months later.

The same can’t be said for Audi, which we reported yesterday would only see hybrid models launched in the U.S. two years after their debut in Europe.

In a separate interview, Herbert Kohler, the chief of Mercedes-Benz’s E-Drive and Future Mobility unit, said the automaker was keen to remain the luxury leader in alternative propulsion systems and would be spending half of its $5.6 billion R&D budget this year on green technologies.

[Automotive News, sub req’d]