We knew that the free Not a Hero DLC was coming for Resident Evil 7, but we didn't know much about it. Capcom has let the "hero" out of the bag now, revealing that Chris Redfield will be coming back to the game.
Note that spoilers are ahead if you haven't already finished RE7.
The tweet is indeed a teaser for the story-based DLC. At the conclusion of the game you find Redfield is working for Umbrella Corp., but the hint seems to be that this weird combo of Redfield and his job could deal with him pursuing a person or a creature. An upcoming CGI movie in Japan called Biohazard: Vendetta reunites Chris, Leon Kennedy, and Rebecca Chambers. The plot has Chris chasing an individual who is trying to release something called The Trigger Virus in New York City. The film is supposed to be a story bridge between RE6 and RE7, so perhaps the DLC let's the player actually pursue the madman.
Unfortunately, Capcom still isn't divulging the release date for Not a Hero, other than the always nebulous "this Spring."