They have their own projects now. Destiny is their first big project away from Microsoft in a long time and I doubt many of them are looking back at "the good ol' days." This is meant to be an ambitious undertaking for them and having an a and b squad divvied up between projects (like Ubisoft Montreal with AC3 and AC4) would take away from their ultimate goal, to create the game they want, or more specifically "they game they always wanted to play, but couldn't." Look, I loved Halo. I have sunk many an hour into the original trilogy as well as a good amount of time in Reach and ODST. However, I'm okay with the split if it means more story, more gameplay, and a little less competitive multiplayer. If I need to shoot my fellow player, I have Titanfall for that.