Hideo Kojima celebrated the seventh anniversary of his studio, Kojima Productions, with an announcement that his team were currently working on a "completely new game, as well as some visual projects.”

The details:

Kojima Productions shared a video through Twitter from studio director and founder Hideo Kojima thanking fans for their support, showing off the team’s new studio, and confirming some projects are in the works.
A brand new game separate from the recently revealed Death Stranding 2 (DS2) was confirmed in the video, with no further information being given. This could potentially be the rumoured horror title "Overdose," which was leaked in June, with an alleged trailer also being leaked in November. The game’s footage reportedly starred Margaret Qualley, who played the role of Mama in Death Stranding.
One of the visual projects is likely the recently confirmed Death Stranding movie adaptation being made in partnership with independent production company Hammerstone Studios. There’s little information on the movie so far, but it’s alleged that it will introduce new characters and lore within the Death Stranding universe.

What else is happening at Kojima Productions?

Death Stranding 2 is still in the works following its reveal at The Game Awards earlier in December. DS2 was confirmed to be a working title, and we have no other information regarding the release of the game as of yet.
As Kojima mentioned in the Twitter video, the new studio that will house Kojima Productions has been completed. You can check out this in-depth tour narrated by Akio Otsuka, the voice of Die-Hardman in Death Stranding. It looks pretty unique and could easily fit into one of Kojima’s game worlds.
Kojima Productions also entered a partnership with Xbox in June 2022 to develop a new title for the platform. No one is sure if this is “Overdose” or not, as there’s not much information surrounding it, but it could very well be.

Kojima Productions confirm new game alongside Death Stranding 2