From BF central:
DICE has announced that the BF4 Summer patch will be coming in September and will be called Battlefield 4 Night Operations, including one night map Zavod Graveyard Shift, based on Zavod 311.
DICE is busy testing the upcoming Battlefield 4 Summer patch right now in the Community Test Environment, and by most accounts the patch should be ready for certification soon, meaning a release is likely at the end of August (since it has to be certified by Microsoft and Sony for console releases).
The Summer update will include night versions of maps Zavod 311, Siege of Shanghai, and Golmud Railway (check out screenshots of the maps here). As usual, the patch will also include various fixes and gameplay tweaks, most notably, a tweak on how fast turrets can move in different vehicles.
Right now DICE is also testing a 60 Hz server tick rate, which improves performance and makes everything snappier. DICE has also stated that they are looking to tone down the tracer bullets that were introduced with the last patch.
We’ll have to wait for a full change-log once the patch is released. If you want a sample of the Summer patch, you can sign up or the Community Test Environment and download the CTE version of the game, where various tweaks and content are tested.