During Activisions 2Q earnings call with investors, it was revealed that much of the Bungie team is already hard at work on Destiny 2. This confirms previous reports that Year 3 (Rise of Iron) would be the last expansion for the first game before the release of Destiny 2 in 2017.
Activision Publishing CEO Eric Hirshberg revealed, "The majority of the team at Bungie is actually focused entirely on creating Destiny 2," when asked about what follows Rise of Iron. Of course, it was revealed just yesterday that SRL Racing and Festival of Lights would also return before the end of 2016.
Rise of Iron will only be available to play on PlayStation 4 and Xbox One so if you haven't made the leap to next-gen, now's the time. Expect more details about the final Destiny DLC to be released later this month at Germany's Gamescom.