A user by the name of Jon Kay posted a video on Twitter showing what appears to be early footage of the next batch of Rainbow Six: Siege DLC.
There has been a long rumored Japanese DLC pack called Skyscraper in the works for Siege, and this appears to be it. The video shows a very Japanese looking interior, but very little in the way of gameplay unfortunately.
There's no official release date for Season 4, but with this leak, it might not be unwise to expect more information soon.