Naughty Dog currently has two projects in development that we know of. There's the The Last of Us Multiplayer, which we'll learn more about this year, and there's something else beyond that — presumably a new property, or a new The Last of Us. And while the wait for any kind of concrete information on the Factions revival has been a drawn-out affair, the developer is actually very wary of revealing its secret title too soon.
In an interview with ComicBook.com, studio boss Neil Druckmann says that announcing a game well in advance can be detrimental to the development team. "We did announce Uncharted 4 and The Last of Us: Part II way in advance, but that actually caused a little bit of the work-life balance issues that we've sometimes had at the studio," Druckmann admits.
He goes on to reference Naughty Dog's unknown project: "By delaying that announcement a bit, we could play with the schedule more and we're more conscious now about how we're approaching production. So there's our multiplayer project and there's another project that I will not say anything about that's beyond that that we're also very much excited for."