The loss of the fan-favorite Destiny 2 Hunter Vanguard, Cayde-6, was monumental for the series. His fall at the hands of Uldren Sov in Destiny 2: Forsaken has sparked many wild theories about how the Exo Hunter could return, despite Bungie stating Cayde-6 is dead for good. Still, one particularly plausible theory posits Bungie could bring Cayde back through a loophole in that promise, albeit in a different capacity.
With Cayde-6's Ghost destroyed during the events of Destiny 2: Forsaken, he's unable to come back from the dead as a Guardian normally would. But Cayde-6 is an Exo - an android with the consciousness of a person implanted into it. Exos can live on almost indefinitely in their mechanical forms, but their memories have to be rebooted a number of times over the course of their lives to avoid dissociating from their adopted bodies. The number in an Exo's name refers how many times they have been rebooted; Cayde-6 has been rebooted six times.
While most of an Exo's memories are lost between reboots - and Cayde-6's memories likely died with him - there is still hope for another Cayde to come back. Europa, the planet central to Destiny 2: Beyond Light, houses the Deep Stone Crypt. This is the original source of all Exos developed by Clovis Bray, and it is said that all Exo minds have their original backups saved there.
Destiny 2: The Death Of Cayde-6 Doesn't Mean The End Of Cayde
If his original backup was revived in a new Exo body, players could potentially see the return of Cayde, though not as Cayde-6. He would not remember his time as a Vanguard or his relationship with the player's Guardian, and chances are he would be even more mischievous (and greedy) in his original state than Guardians remember; this "Cayde-7," or potentially "Cayde-1," would have missed out on the personal growth he experienced through his hardships and loss as a member of the Vanguard.
From a narrative perspective, though, why bring Cayde back at all? Uldren Sov has, of course, returned and been redeemed as Crow, and many believe he will take the open spot as the new Hunter Vanguard. Perhaps with the encroaching Darkness of the upcoming Destiny 2: The Witch Queen DLC, a young, naïve, more cutthroat Cayde could be brought back and tempted with its power to fight against the people he no longer knows. This would be a powerful tactic to employ against Destiny 2's Guardians and Vanguard, as no one would want to harm Cayde, just as so many wanted to hurt Crow.