All future BF4 content, including the upcoming Gunmaster game mode and night maps, will be free for both premium and non-premium players.
Some good news for fans who are still enjoying DICE's modern military shooter, Battlefield 4: all future DLC for the game will be made available to both premium and non-premium players completely free of charge. DICE's David Sirland confirmed that all future content for the title, including the upcoming "Gunmaster" game mode as well as new "Night Maps" won't have any cost attached to it.
In addition to these major updates, upcoming content for Battlefield 4 includes several new weapons, a "community map," and another "classic" Battlefield map remake. There's no additional content planned beyond that but it should ensure a steady stream of free updates for Battlefield 4 players.
This can only really be lauded as a good move for EA. With Hardline having just been released, and Battlefront in the works for release later this year, many assumed that Battlefield 4 would simply go the way of every Battlefield title before it, and fall to the wayside.
The promise of additional new content - completely free to boot - shows that DICE is dedicated to supporting it's "older" titles (Battlefield 4 was only release 2 years ago, in October, 2013).
Source: BF4 Central