The director himself has confirmed this on his official Instagram account description. It says: “Neil Druckmann, Co-Studio Head, head of Creative Naughty Dog; Executive Producer The Last of Us HBO; Writer/Director unannounced game.”
While Druckmann has not made any statements yet, this new change ticks some of the theories that many fans have been gathering recently. There has been strong speculation that this unannounced game is The Last of Us: Part 3 but bias might be part of it. There has been talk that Naughty Dog has been working on a new intellectual property recently and the anticipated standalone multiplayer spin-off has been reported to have gone back to square one so these two theories are more sound right now.
For how long it is going to take for Naughty Dog to announce either of these two officially is still up in the air though. Still, the PS5 development cycles are now increasing so it could take a while before that big announcement.