Bungie wants to give players the chance to play with the default mods in their current state, as the Lightfall expansion will bring some major changes with it. At the same time, the promotion does not apply to seasonal artifacts and modifiers obtained during raids.
And next week, the cost of focusing Trials of Osiris, Iron Banner, Crucible, and Gambit gear will drop to 25 Legendary Shards and the cost of Focusing Crafted Weapons to 50 Legendary Falcons.
Bungie also announced that Grandmaster Nightfalls will be in the game on January 17th. Activity will become more accessible to all players, while retaining complex content. Developers will reveal more information in the near future.
Destiny 2: Lightfall is coming out February 28th.