It's been a while since we've seen the next-generation Mercedes-Benz C-Class lineup, but testing and development is very much ongoing. Our spy photographers were recently stationed outside a Mercedes testing facility in Germany when a 2021 C-Class prototype suddenly appeared. Its test driver clearly knew our photographers were there snapping images; he waved his hand as he drove past.

Although the test mule remained heavily covered in camouflage, we do know several facts about it. For starters, it's built on an updated version of the current C-Class RWD platform, so expect it to have roughly the same exterior dimensions.

However, thanks to some clever engineering and design, interior space will expand for both passengers and cargo. Mercedes also made these platform changes in order to accommodate the new plug-in hybrid system. A series of four- and six-cylinder engines will be found under the hood once again, including gasoline and diesel, but the PHEV system is key to not only improved fuel economy but also power output. What will be very interesting to find out is whether the next-generation AMG C63 will be a PHEV. We wouldn't at all be surprised if it is.

Another key feature C-Class owners will benefit from is the latest version of the automaker's MBUX infotainment system. It's already available on the newly refreshed E-Class sedan and, later this week will debut on the facelifted E-Class coupe and convertible. Expect the new C-Class to feature a fully digital dashboard and plenty of connectivity features like Apple CarPlay and Android Auto integration.

As per tradition, the new C-Class sedan lineup (not including the AMG versions) will debut first, followed by the coupe and convertible in about a year's time. In Europe, there'll be a wagon version and it's entirely possible an All-Terrain variant is in the works. In the US, the Mercedes E-Class All-Terrain replaces the E-Class wagon for 2021, but given that the C wagon isn't currently sold here, it's unknown whether an All-Terrain is in the cards for this market.

Expect the new Mercedes-Benz C-Class sedan to debut in the coming months.