This seems to be the rumor going around lately. Uncharted IV was a pretty definitive end for Nate, and although Lost Legacy was a success the plans to do spin-offs featuring Cassie, Sam, Sully, or even Cutter never really materialized, probably because a lot of ND's resources have gone back to the "Last of Us" since. There was the PC port and the PS5 upgrade-both probably done to tie in with the movie-but that's it.
The new sequel will reportedly be a reboot (Maybe like the movie was, an 'origin story' of sorts although one that doesn't line up with the games continuity unless you totally ignore 3's prelude) and not involve Naughty Dog but Sony and perhaps a new studio.
Kind of curious if it'll be more "open world", something they kind of experimented with a bit in 4 and LL but still having a linear story. Maybe it'll be similar in a few ways to the Tomb Raider reboots (although probably not as incredibly gory and brutal as those tended to be-Uncharted is mainly supposed to be fun so a gritty reimagining would not be the best idea) in which the last two games were fairly open, kind of had a 'hub' area like God of War (although LL sort of had that).