While we know for sure that Destiny 2 is going to happen - it was confirmed some time ago - we've never been given a clear time frame as to when it might make an appearance.
Legal documents from before the launch of the first game back in 2014 suggested that Bungie we're going to try and ensure a release of a core title every two years, and by that reckoning that would mean the launch of Destiny 2 later this year. However, according to reports, this isn't likely to happen, and the full sequel to Bungie's online shooter is most probably going to hit sometime in 2017.
There's nothing particularly unusual about a delay of this sort, but it comes at a time when Destiny itself is at a crossroads, with Bungie unable to offer a clear direction for the game looking ahead. Invested fans are concerned about the lack of upcoming content, and the studio aren't doing themselves any favours in terms of their communication with the community, as exemplified by the recent fallout over the switch to skill-based matchmaking.