Mexico looks set to lose its place on the F1 calendar.
It is a highly popular race, but organisers are yet to agree a new deal with Liberty Media for 2020.
Liberty needs to axe two existing races to accommodate Zandvoort and Vietnam, having capped the calendar at 21 races for next year.
Asked if the calendar might be expanded, Hockenheim spokesman Jorn Teske told Kolner Express newspaper: "No. No increase has been suggested so it stays at 21 races.
"Apart from us, also Mexico City and Barcelona have no contract," he said.
"It looks like Silverstone and Monza have new contracts," said the Hockenheim spokesman.
"But we also have to wait and see if the people at Zandvoort can make their track suitable for Formula 1 in time. It is an ambitious goal," said Teske.
The German GP this year was rescued by sponsor Mercedes, but Teske would not be drawn on whether the same is also true for 2020.
"We are not talking about Mercedes, we are talking about Liberty Media," he said.