Hideo Kojima is working on at least two games right now with Kojima Productions. The first one is an Xbox-exclusive that could be Overdose.
The other one is Death Stranding 2, which Norman Reedus has already teased last year and earlier this year. Elle Fanning is believed to be a part of the said game. Neither have been fully revealed so far, but it appears Kojima is getting ready to confirm Death Stranding 2 at The Game Awards.
Before anything else, let's address the elephant in the room. People don't need rumors to theorize Kojima's involvement in any event by Geoff Keighley. The two are good friends and Kojima has often used Geoff Keighley's events to reveal his latest project in the past. Case in point, Kojima attended last year's Summer Games Fest to reveal Death Stranding: Director's Cut.