Prototypes for Mercedes-Benz’s next-generation S-Class have been spotted again.

The car is expected to debut at the 2019 Frankfurt International Motor Show in September and should be in showrooms in 2020 as a 2021 model.

From earlier test mules, we know the size and proportions will match up with the current model but there will be a slightly wider track, and it also looks like the hood will be lower and longer. This should give the car an impressive stance.

2021 Mercedes-Benz S-Class spy video from Motor Authority on Vimeo.

The current Mercedes-Benz S-Class, the W222, was introduced for 2014 and immediately rocketed to the top of the sales chart. The six-figure sedan racked up more than 100,000 sales in its first year and that was before the arrival of additional body styles such as the 2-door cars and extra-long Maybach and Pullman.

It’s clear the new S-Class has some big shoes to fill. Luckily for it, it will adopt a new platform, in this case Mercedes’ MRA design for rear-wheel-drive cars. The current S-Class rides on an updated version of its predecessor’s architecture.

It’s hard to gauge what Mercedes has in store for the new S-Class this early out. The current model just received its mid-cycle update for 2018 so understandably Mercedes is shy to talk about the next one. We already know a few things, however.

2021 Mercedes-Benz S-Class spy shots - Image via S. Baldauf/SB-Medien

2021 Mercedes-Benz S-Class spy shots - Image via S. Baldauf/SB-Medien

Every powertrain will be electrified, either with mild-hybrid or plug-in hybrid technology, and most engines will either be a 3.0-liter inline-6 or 4.0-liter V-8. It’s not clear if there will be an electric version as Mercedes is working on a large electric sedan under the EQ sub-brand.

But getting back to the new S-Class, there will also be much more advanced self-driving systems, including perhaps a Level 3 system. This is where the car can handle its own in certain situations, leaving the driver free to do other things. However, the driver will need to be ready to take back control at a moment's notice. Audi has already introduced such a system in its latest A8, though it isn't available in the U.S. due to a lack of regulations.

Inside the dash will still consist of a dual-screen setup, but the secondary screen will increase dramatically in size and be mounted in a portrait orientation. At the bottom of the massive screen will sit one row of buttons with the rest of the controls relegated to the touchscreen interface.

2021 Mercedes-Benz S-Class spy shots

2021 Mercedes-Benz S-Class spy shots

We also expect Mercedes to offer the next S-Class in multiple body lengths, from a short wheelbase right up to the extra-long Pullman. However, there’s a good chance the current S-Class Coupe and Cabriolet will be phased out. A roomier next-generation SL-Class with 2+2 seating is expected to fill the void.

S-Class rivals include the Audi A8, Bentley Flying Spur, BMW 7-Series, Genesis G90, Jaguar XJ and Lexus LS.

Stay tuned for updates as development continues.