All there staff except the live team have been working on destiny 2 since October 2014, Bungie even announced that themselves. Keep in mind to what they are working on is up in the air. They announced a vex and cabal expansions for TTK but, now have been removed from the mix and nothing has been said since they announced no new content till D2, so you can probably imagine what D2 will consist of, I bet us it's either vex or cabal, take your pick.