Naughty Dog has announced that the Uncharted 4: A Thief’s End multiplayer will occur from December 4th until December 13th. However, to get access you’ll need to own the Uncharted: The Nathan Drake Collection as well have an active PlayStation Plus membership. Details about the actual beta, game modes or maps have not been revealed yet.
TheUncharted: The Nathan Drake Collection is only a few weeks away from release, and will be available in North America from October 7th, and October 9th in Europe. A demo for the game will also be releasing on September 29th 2015, so you can try the game out before committing to a purchase.
You can expect more details on the beta closer to December.