Audi will reveal the long-awaited sixth-generation A6 saloon and estate tomorrow (31 July), making the landmark switch to electric power for one of its longest-running and most successful models. 

The radical new Audi A6 E-tron has been previewed – in both Sportback and Avant bodystyles – in concept form, and a new preview image (below) suggests the production versions will stay remarkably close to those striking show cars, as has also been suggested by recently spotted prototypes.

The unveiling of the C9-generation A6 will come 30 years after the launch of the original A6, though that car's predecessor, the 100, dates back to 1968. 

The A6 E-tron will be Audi's fifth pure-electric model line, and will be closely followed by electric successors to the A4, A8 and A3.

The combustion-engined A6 that's on sale today will be heavily updated and rebadged the A7 in the coming months, with Audi retiring the luxury four-door coupé that currently uses that name.

The newcomer rides on the new PPE architecture that Audi has co-developed with Porsche for use in premium electric cars, as already deployed for the Q6 E-tron and its Porsche Macan Electric sibling. 

​Audi hasn't yet given full details of the drivetrain, but the specifications will likely mirror those of the Q6 E-tron, which offers 396bhp and a 100kWh battery in '55' trim, and is equipped with 800V charging architecture, which means faster charging and less weight.

Elsewhere in the range, there will be a choice of performance-oriented dual-motor set-ups – including an S6 and RS6 – and efficiency-minded, rear-driven variants offering 0-62mph times ranging from “well under” 4sec to 7sec.

The Q6 has a circa-100kWh floor-mounted battery that gives a range of 435 miles and the ability to charge at a rate of 270kW, which allows it to gain 186 miles of range from a 10-minute top-up. Assuming it comes with the same battery pack, the A6 is likely to improve on that headline range figure by virtue of its lower, sleeker body. 

The A6 Avant E-tron was spotted testing on roads around Germany earlier this year, with visible details including its slim daytime running lights sitting above the main headlights, a large front grille, cameras to replace its rear-view mirrors and completely redesigned rear lights with a light bar.

It also has door handles also sit regressed into the bodywork – not shown on the concept – and new, aerodynamically optimised alloy wheels. 

Because the battery is sited flat and arranged across the chassis, the earlier concept version of the A6 Avant E-tron is said to offer broadly comparable interior dimensions and load capacity to the current A6 -  a trait that will likely carry over to the production car.

Importantly, the electric concept shows how the longer wheelbase afforded by an EV platform allows for more leg room in the front and rear.

The A6 Avant E-tron measures 4960mm long, 1960mm wide and 1440mm tall, which makes it roughly the same size as its ICE forebear.

In an interview with Autocar last year, then Audi design boss Marc Lichte said: "The A6 E-tron [will launch] exactly three years after we launched the E-tron GT, and on the A6 E-tron – as you could see on the concept car, which is very, very, very, very, very close to the production car – you can see that we will go sleeker and simpler."

Following on from the A6, the new A8 E-tron – due on the roads in around 2027 – will be "very close" to 2021's Grandsphere concept, according to Lichte.

He also strongly hinted to Autocar that the new Audi Activesphere concept could become an 'Allroad 2.0' version of the next Audi A7 in 2027.