The Division's new expansion, Underground, is live now as part of patch 1.3. As the name suggests, Underground owners will be heading down, down, far underground into the tunnels of New York—tunnels which lend themselves to procedural generation and custom rulesets in the form of Directives.
Would-be spelunkers were reporting that The Division was failing to acknowledge their season passes, shutting them out of Underground, but Ubisoft appears to have resolved the issue. Now players just have to contend with Delta errors and extended queues. Both are under investigation.
If you're not planning to jump into Underground, patch 1.3 brings a wealth of changes, from new high-end weapons and gear, a new Dark Zone bracket and a massive overhaul to existing weapons (acquired after patch 1.3) that aims to make the likes of shotguns and LMGs more appealing.