During their Destiny livestream yesterday, Bungie announced that the Age of Triumph event will begin on Tuesday, March 28 on PlayStation 4 and Xbox One.
With Age of Triumph, Bungie will bring back the Vault of Glass, Crota?s End, King?s Fall, and Wrath of the Machine raids, and all of them will be at 390 light level. Some of the old rewards are coming back (and they can all drop at up to 400 light level), and there will also be some new ornaments and other rewards, including Ghost skins and Sparrows.
There will be some improvements to the raids, with Bungie saying the Oracle encounter in Vault of Glass has been shortened slightly, and changes have been made to Crota’s End (details TBA). You’ll also find new challenge modes for the raids, and there will be a different featured raid each week: Crota’s End is week one, Vault of Glass is week two, King’s Fall is week three, and Wrath of the Machine is week four. Bungie added that the overall light level isn’t increasing past 400, because they want to give every player the chance to reach the cap with Age of Triumph.

Destiny 2 is releasing this fall, and Age of Triumph is the final live event for Destiny 1, but as Bungie Community Manager David Dague told IGN recently, the first game will continue to be supported by them:
Our plan is to continue to support Destiny 1 for the foreseeable future.
Dague also addressed the announcement that your Destiny 1 power and possessions won’t carry...