EA's Battlelog has details on Battlefield 4: Legacy Operations, a free DLC pack coming soon to Battlefield 4 for Windows, PlayStation 4, and Xbox One. At the center of the release is Dragon Valley 2015, an updated version of the Dragon Valley map from Battlefield 2, saying this "opens up for vehicular mayhem on land, air, and sea, with a massive number of flags, and destructible and repairable bridges." This trailer shows off some play testing of the map, and here's a bit on how the original had to be changed:

If you played Battlefield 2, you likely remember the map – it was huge, with a massive number of flags, and destructible and repairable bridges. Our goal for this map is to make a great, large vehicle map for Battlefield 4 but at the same time modernize the original where appropriate.

Some things had to change when reimagining the map. Battlefield 2 featured a poor draw distance (how far you can see in the game world) by today’s standards, and the original map was built around those limitations. We tackled this in several ways: first we increased the terrain verticality to closer mimic a real life Chinese river valley – and to give us more terrain occlusion for long distances, especially on the central island. We also added a dynamic cloud layer, which not only adds a welcomed air-to-ground separation in terms of gameplay, but also helps shroud far distances at ground level. This has the added bonus effect of allowing you to have intense aerial firefights above the cloud level, which looks really, really cool in Battlefield 4.