Destiny expansion packs aren’t filled with scripted events, and the gameplay loop and just doing the same mission over again. The game missions are linear so they don’t require much thought other than looking cool. The enemy AI doesn’t change, and new enemies are just reskins of existing enemies. They add a ton of armor skins for the store, but I’m pretty sure most of the staff aren’t artist. With the quality of the content they release 800+ people seems excessive.
WTF is Bungie doing with those 850 people?
As I mentioned, they doesn't only work in Destiny 2 expansions. This year they will release a new game called Marathon, in addition to a Destiny mobile game developed with Netease. Plus are also working on movie & tv show adaptations of Bungie IPs.
Plus are also working in a new IP that will use the PS Studios publishing label instead of Bungie (which could also be released in a year or so).
This is the announced stuff, and also recently mentioned they'll focus in Destiny and Marathon IPs as they move their new IP to PS Studios.
The logical step after releasing all this stuff would be Destiny 3, which pretty likely they may have already been considering and trying to conceptualize or prototype in many ways. But since Destiny 2 continues in the top grossing rankings of PC every year pretty likely continues making a lot of money may have decided to push Destiny 3 back and may want to continue milking D2 for some years more while focusing on releasing and supporting their other two new games.
Who knows. If Microsoft were really happy with Pentiment then it makes sense for them to approve something again like that, but it seems like OW2 and Avowed had them at capacity.
Games like Pentiment or Avowed weren't greenlighted by MS, they already had them before the acquisitions. Outer Worlds 2 would be the first project greenlighted inside MS.
Regarding MS being happy with Pentiment, they also mentioned to be very happy with Hi-Fi Rush, another well reviewed smaller game that didn't sell a shit. And shortly after it they did shut down their studio.
I assume going forward MS will focus on games with bigger sales potential.