I've heard rumors that after destiny, bungie is done, gone. So maybe they simply fired Marty after they finished destiny so he could go work for someone else, I mean if this is their last game they don't need him anymore, and I'm sure they figured some other company would love Marty to work for them. Just a thought.
... That isn't a rumor. That isn't a thing at all. Bungie has a contract for three more games after Destiny, and after that they'll likely just move onto something else. Spreading rumors does nobody any good. That's how we get spammed with threads about "Oh Bungie you said the Beta would be in 8 weeks and it isn't here you all suck'' type threads.