I've put this tweet in Google translate:
"・・と、こんな感じです。無料アップデートの一週間後のDLCにはレースカーパックやコースパック、レーシングギアパックなどを準備中です。それはまた次の機会にお知らせします。連投すみませんでした。"
And this came out:
"And · ·, looks like this. One week after the DLC track pack is a free update pack and race cars, racing gear is being prepared and packed. It also will be announced at the next opportunity. I'm sorry consecutive pitching."
Of course google translate is not so accurate in grammar, but I believe it's going to be a free DLC