It looks as though the online multiplayer for Uncharted 4: A Thief's End may not be making its way to the upcoming PS5 and PC re-release.
No multiplayer in Uncharted: Legacy of Thieves Collection, uncharted pc gameplay
Uncharted 4: A Thief's End New Gameplay Preview Video Showcases, uncharted pc gameplay
PlayStation Studios' future — what to expect?, by Ryan
Naughty Dog is in danger of missing the boat with the PS5