The trailer is one of tone-setting rather than a reveal of features or gameplay. It opens with a closeup of Cayde-6 looking like death on toast and apparently at the mercy of an Awoken Hunter—possibly Abra Zire, although she was (according to the Destinypedia, anyway) killed at the Battle of Saturn during the Taken War.
(That may be a bad theory: It's been pointed out in the comments that the shooter looks far more like Uldren Sov, brother to Mara Sov, Queen of the Reef. We pondered his possible involvement in the Forsaken expansion last week.)
Whoever it is, they're wielding the Ace of Spades hand cannon, a quest item that was added to the original Destiny in the Taken King expansion. The trigger is pulled, Cayde goes down, and several presumably-bad guys walk out. Is that the end of our hero?
I'm guessing not: The image at the end of the trailer shows him being carried away, and since having his arm blown off at the end of Destiny 2 didn't seem to bother him much I'm guessing they'll be able to fix up his face, too. We'll find out on September 4 (or thereabout), when Destiny 2: Forsaken goes live.
Update: I completely forgot about this, but rumors of Cayde-6 dying in Destiny 2 actually surfaced back in October in a datamining thread on Reddit. The Future War Cult and New Monarchy factions were found to have lines referencing his death and "what comes after," and there are also mentions of the Reef and the Prison of Elders, the setting for the Forsaken expansion.
It obviously doesn't confirm that Cayde-6 will be leaving is, especially since other elements of the thread are off the mark—Osiris was said to be returning to the Tower, for instance, and that didn't work out. But it's close enough to the mark to make this trailer, and the possibility that Cayde-6 might actually be dead, a whole lot more interesting.