As spotted by Polygon, Destiny 2's Haunted Forest game mode is likely going to be making a return this year as part of the Halloween-themed Festival of the Lost. The reveal was made by the description of two emblems granted to last year's participants in the game mode.
The "Terror’s End" and "Deep in the Woods" emblems from the 2018 Festival of the Lost tracked progress towards terrors defeated and lowest branch reached in the Haunted Forest last year. Those emblems were updated sometime since the release of Destiny 2: Shadowkeep and now show progress for both 2018 and 2019. Since the Haunted Forest hasn't been available so far in 2019, players are of course assuming it will be making a return as part of further Halloween festivities this year.
The Haunted Forest mode from last year's Festival of the Lost challenged solo players and fireteams to get as far into the forest as possible in 15 minutes while taking on increasingly challenging groups of enemies.
We already knew thanks to the updated Destiny 2 roadmap that the Festival of the Lost would be returning from October 29 to November 19. The updated emblems seem to confirm that the Haunted Forest will be coming along with it, likely with some other new rewards for players to earn like last year.