I don't think they can use the IMS oval and road course configuration that close together as a lot of work needs to be done to go back and forth. Homestead, Daytona, and Charlotte can all be used with little changes, though, so they could be done on the same weekends.

However, the DTM USA series doesn't really have much to do with VW in NASCAR, who seem to be against the idea, calling it "entertainment" and "short term" just a few days ago:

"We are now at a major deciding point in motor sport history to precisely define where motor sport is going," Baretzky emphasized. "If we go strictly in an entertainment direction like NASCAR and IndyCar are going it is a short term solution and it will not last very long."
I'd love to see it, but I don't think it fits in with VWAG's ideas for the future of racing.