I didn't make this post in haste because I wanted to be completely sure I knew what I was talking about before discussing this topic. Here are the OG Halo devs that are still working for Bungie.
Jason Jones - Does he even make games anymore? After Halo 2 he stopped getting actively involved in game development and took the role of studio management. But in 2013 he scrapped the original version of Destiny because it was "too linear", made a team called "Iron Bar" lead by Christopher Barrett to release the Year 1 version of Destiny. After that he let others like Luke Smith lead the game and resigned himself from game development again.
Joseph Staten is the guy who wrote the story for Bungie Halo games and also the cinematic director.
He left Bungie because his version of Destiny was scrapped and instead we got a mess in 2014.
The new writers that were bought in after the original writing team left preferred Staten's original story and put it in the Grimoire Cards. A lot of the leaks from the original version of Destiny coincide with revelations in Shadowkeep, so the story is still being based on some lore blueprint left behind by Staten. The backstory of Savathun(antagonist of Witch Queen) was first provided in Book of Sorrows and it also hinted about "The Final Shape" which is supposed the last expansion of Destiny 2 and is supposedly where the original 10 year story ends.
Lars Bakken - Halo 3 Multiplayer Designer and Halo Reach Co-op lead
Tyson Green - aka Ferrex
Chris Butcher - Management and overseeing new IP
Ben Wallace - Seems to be working with Chris Butcher
These four joined after they left Microsoft and the OG trilogy, had minor roles in ODST/Reach but major roles later in Destiny
Alex Pfeiffer - Designer in Halo ODST/Reach. Now Design Lead.
Derek Carrol - Credited as a multiplayer designer in Halo Reach and "... And the Rest of the Bungie Crew" in ODST. Now Senior Designer.
James Tsai - Designer of Firefight in Halo Reach. Now Director of Witch Queen.
LinkedIn mentions 1154 people working in Bungie. So barely 1% of the OG Halo crew is still working in Destiny. Not a single person from the OG writing team has remained, although quite a few engineering/tech leads are here. Its very disingenuous to try to pretend you have the "original developers of Halo who launched the Xbox" without any of the recognizable names like Joseph Staten, Marcus Lehto, Marty O'Donell or Max Hoberman(I get Jason Jones, but he has resigned himself from game development anyway). This is the same as "Back 4 Blood - from the creators of Left 4 Dead". I see people in twitter or even here believing that the original creators of Halo are making the next big thing(some even think it would be as popular as GTA or Fortnite). I can't see Bungie making a new original sci fi IP with lore on par with Halo or Destiny without there original writing team.