According to a report by Jason Schreier at Bloomberg, a new Uncharted game could currently be in development at Naughty Dog.
Bloomberg's report, which takes a look at Sony's first-party studio structure and how the company is shifting focus towards AAA hits only, states that Sony Bend (the Days Gone development studio) were helping with a new Uncharted game before moving project.
The report states: "one team at the studio was assigned to help Naughty Dog with a multiplayer game while a second group was assigned to work on a new Uncharted game with supervision from Naughty Dog."
"Some staff, including top leads, were unhappy with this arrangement and left. Bend's developers feared they might be absorbed into Naughty Dog, and the studio’s leadership asked to be taken off the Uncharted project."
"They got their wish last month and are now working on a new game of their own."
However, Schreier doesn't know whether that game is still in development. His information has come from Bend, rather than Naughty Dog, so he doesn't know if the project is still ongoing.
I guess we'll have wait and see if an announcement comes from Naughty Dog or PlayStation sometime soon.
While the report also states that Naughty Dog are working on a remake of The Last of Us, their next game has not been officially revealed.