As per the Bethesda post
"Bethesda Game Studios is releasing a free Fallout 4 update for download on Xbox Series X|S and PlayStation 5.
This free update includes native applications for PlayStation 5 and Xbox Series X|S, Performance mode and Quality mode settings, as well as stability improvements and fixes. Experience up to 60 FPS and increased resolutions!"
Bethesda has promised the update for some time but now states that as long as you own the current series of hardware from Playstation 4 and Xbox One forward, you will be able to get the update for free.
Some information on what it adds for PC players-
Widescreen and ultra-widescreen support
Fixes to Creation Kit
Quest updates
It also includes the Enclave Remnants storyline and items.
Enclave Remnants brings the Pre-War cabal, The Enclave, into the Fallout 4 storyline. In this new quest, “Echoes of the Past,” can you stop The Enclave from spreading their dangerous ideology and gaining a foothold in the Commonwealth?
And the Halloween Workshop
Leftover from an ill-fated Halloween party, thrown by the New England Technocrat Society, these 38 new Halloween decorations include witches, cauldrons, ghouls and more! Decorate for Halloween or make your settlements spooky all year round!