Audi motorsport boss Dieter Gass says DTM will need to have at least 16 cars on the grid once Mercedes leaves the series at the end of the current season.
Mercedes’ exit will leave only Audi and BMW as constructors for the German touring car series – though Aston Martin may join in 2020.
At present the grid is made up of 18 cars – six from each of the three manufacturers – after the trio agreed to scale back from having eight each before 2016.
From next year, BMW and Audi will have to return to putting out eight cars each, according to Gass.
"That's the discussion we are currently holding," Gass said when asked by Autosport about next year's likely grid numbers.
"It's early days still, but I think we need to try at least to have two [extra] cars from each manufacturer on the grid. For me that's very much the [minimum] limit."
Gass also suggested that the extra cars could be run by customer teams, rather than Audi directly, albeit with access to latest-spec factory equipment.
"Currently I'm planning to get proper customer cars, which is as well the target of Gerhard [Berger, ITR chairman], to get more independent teams involved," he said.
"That's the big difference to what customer cars were in the past, [they were] previous years' cars. [Next year] there will be no previous years' cars, the material will be factory material, basically."
Next season marks the first year of the DTM's new regulations, in which the series will adopt a common rulebook with the Japanese Super GT series.