I would guess mid-January. I think once the online is more stable and the special seasonals have been taken down, they will introduce a larger batch of paid for content. However, I am already very impressed at PD's commitment to giving us something new every Thursday; the Mercedes AMG Vision GT the day before release, the BMW M4 the next week, and then Mario Andretti's Hudson! Back on topic, we already know PD have a shed load of content in the pipeline, so I guess it will sooner rather than later when it arrives!
