Speaking to GamesBeat, Phil Spencer stated that he will be in charge of overall strategy for games while Matt Booty will handle the actual execution of these games.
After Phil Spencer was promoted to the role of executive vice president for games, his previous post was left open.
Matt Booty has been working at Microsoft as the head of Minecraft and now he has been promoted to be the corporate vice president of Microsoft Studios.
This is the position which Matt Booty will occupy from now on.