From these IGN articles, it seems ND has sacrificed multiplayer for a better single player experience:
"In an interview with USG, Naughty Dog lead game designer Emilia Schatz explained the decision to not include a multiplayer mode in the highly-anticipated The Last of Us sequel. 'Were focusing on a single-player experience, so were just making a single-player game for this,' Schatz said."
It looks like Naughty Dog is evolving in how they make a linear game with open world sections similar to UC4:
"The developers are taking a similar approach the studio has in its most recent games like Uncharted: The Lost Legacy and Uncharted 4: A Thiefs End, with a wide linear design to the world."
"The best example of this in my demo was a portion of the Suburbs, in which I could have simply run into one building, exited out the back door, and moved onto a new area. Instead, by exploring every structure, I not only found additional supplies but also a back alleyway with a small environmental puzzle, as well as a nest of runners to tackle."
TLOU2 will have a lot more potential with this format because of its incredibly fun scavenging and upgrade systems.
From the small gameplay snippets shown, TLOU2 is looking a lot more versatile, with its traversal, stealth, complex enemy AI, dogs, dodge button, jumping mechanics & new types of infected enhancing the core gameplay.