The convertibles of today are generally known as little two-seat roadsters like the MX-5 and S2000. But it wasn’t long ago that a different kind of beast cruised the ocean promenades - the four door luxury convertible. According to Motor Trend, Mercedes-Benz is set to revive the tradition with a production version of the S600-based Ocean Drive concept due by 2011, however, Audi is also expected to join the party with its new A7 four-door convertible due around the same time.

The Ocean Drive concept that was unveiled at January’s Detroit Auto Show was based on the current Mercedes S600 sedan’s running gear, so it’s likely any production version will be the same. Being a Mercedes flagship, base models will start with the new 5.5L V8 with top-end cars getting the biturbo V12 and possibly AMG’s hand-built 6.2L V8.

Four-door convertibles haven’t been popular since the 1960’s, where cars like the Lincoln Continental drop-top roamed the streets. Part of the reason why most manufacturers haven’t produced them in volume is because of the extensive structural modifications required to stop them from flexing too much. Not only does it add significant costs to the development, but the cars also suffer from poor dynamics due to the extra weight of the modifications.

There’s still some doubt as whether the car will finally be produced. Mercedes is also rumored to be developing a convertible version of the CL mega-coupe as seen here in this rendering, which could cuase some cannibalization of sales as both cars are tipped to cost around $120,000.