Thanks to a recently discovered exploit, the return of Destiny's Trials of Osiris has been delayed.
The exploit extends the length of the Hunter Nighstalker's Shadowshot Super by allowing the player to reset it when they wear a specific Exotic helmet and enter their option menu while the timer is active. With Trials of Osiris being an extremely competitive PvP mode that rewards match win streaks, you can see why this would be a problem.
Addressing the issue in this week's Bungie Weekly Update, David 'DeeJ' Dague wrote:
This week at Bungie we’re talking about your rematch with Oryx, the return of Trials of Osiris, and (you guessed it) we’re talking about Shadowshot.A funny thing happened on the way to the Lighthouse. It turns out that there’s a particularity nasty bug that would undoubtedly conspire to create a less competitive return to form for Trials of Osiris. We’re going to be intentionally vague here, for what we hope are obvious reasons!We’re going to disable that bug before we invite you to take your next run at a 9-0. We’re also working on a final fix for the bug itself as soon as possible. As soon as we have a solid commitment for Brother Vance, we’ll make a formal announcement on when Trial of Osiris will begin again. We hope that most of you recognize the impact a limitless Nightstalker would have on the competitive landscape.Thanks for your patience.
It's disappointing, but at least it gives you more time to focus on the currently ongoing Iron Banner event. When Trials of Osiris does return, there will be a number of changes with it which you can read up on here.