"Rally the Troops", indeed.
It seems a Cabal invasion will destroy
The Last City, forcing Guardians to flee, and also lose all of their hard-earned gear and loot. The trailer features a retelling of the city's fall from two viewpoints - the stoic Commander Zavala (Lance Reddick), leader of the Titans and Cayde-6 (Nathan Fillion), headmaster of the Hunter Vanguard.
Also, based on Zavala's recount, the trailer seemingly implies that a lot of your favorite NPC Guardians (and maybe Ikora Rey (Gina Torres), leader of the Warlock vanguard) perish during the battle. That's all fine and well, just as long as Lord Shaxx (Lennie James) made it out alive!
All jokes aside, the new trailer also confirms that Destiny is finally making the jump to PC with the sequel as well as confirming a September 8 worldwide release. Pre-ordering will also grant you early beta access.
Here's the official description of Destiny 2 from Bungie:
The fight to take back our home begins September 8th, 2017. Pre-order Destiny 2 to get early Beta access. From the makers of the acclaimed hit game Destiny, comes the much-anticipated sequel. An action shooter that takes you on an epic journey across the solar system. Humanity’s last safe city has fallen to an overwhelming invasion force, led by Ghaul, the imposing commander of the brutal Red Legion. He has stripped the city’s Guardians of their power, and forced the survivors to flee. You will venture to mysterious, unexplored worlds of our solar system to discover an arsenal of weapons and devastating new combat abilities. To defeat the Red Legion and confront Ghaul, you must reunite humanity’s scattered heroes, stand together, and fight back to reclaim our home.