At Dead or Alive Fest 2019, in addition to Rachel making it into the game as DLC, there were also a couple of other interesting announcements made about future content for Dead or Alive 6. The first announcement is that there will be new DLC costumes from Gust games, with Atelier Ryza being a primary example. The second announcement is that a character from Dead or Alive Xtreme: Venus Vacation, a free to play browser game, will be making an appearance as a DLC fighter in Dead or Alive 6.
You can find the tweets making the announcement below:
Dead or Alive 6 is available now for PS4, Xbox One and PC.
Source: doa6jp (1), (2)