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.
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.
Michael Salvatori - While Halo's music is attributed Marty O'Donell, many iconic tracks like
A Walk In The Woods had the involvement of Michael Salvatori providing assistance to Marty. Michael Salvatori appeared in many interviews alongside and acted as his assistant.
I liked Destiny 1 music more than Destiny 2 music(but Destiny 2 music had its moments). Destiny 1 music had this "mysterious tone" that Destiny 2 lost and was more focused in "heroism". Bungie used Marty's Music of the Spheres in Destiny 1 without crediting him which led to lawsuits. I see a lot of the OG Halo devs like Marty, Marcus Lehto(designed the original prototype of Destiny) or Joe Staten never mention Destiny but happily talk about Halo.
Christopher Barrett - Not involved with Destiny since Rise of Iron. Has been working on a new IP.
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
Zach Russell - QA/Programming and Tech
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.
Mark Noseworthy - Engineering Producer at Halo Reach, but was already Gameplay and Campaign preproducer in Destiny at the time. Now Vice President.
James Tsai - Designer of Firefight in Halo Reach. Now Director of Witch Queen.
These people were not Halo devs but still part of old Bungie studio.
Pete Parsons - Then Studio Head, now CEO. Had the same role that Bonnie Ross now does at 343i.
Luke Smith - Every Destiny fan knows this guy. He was originally a freelance writer for Kotaku and then a news editor at 1up.com. He was known for his lengthy article focusing on problems in Halo 2. He joined Bungie in 2007 as a for writing the Bungie.net content updates. He became a Design Lead in Destiny and Game Director in Destiny 2.
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. It would be embarrassing if their next IP is marketed as "from the creators of Halo", with Destiny it made since some were still around till Destiny 1 launch.
And people speculate about how Bungie will be handled comparing them with Rare, how not much of the OG Rare crew is still present but Bungie will be different. But they already are in a position worse than Rare hardly retaining anyone from the OG team.