Microsoft Studios was a catchment company for all of Microsoft's first-party Xbox games. However, through 2018, and indeed before, the company acquired numerous game developers and studios. Last year was particularly busy with several new companies joining the Microsoft Studios fold. To emphasize this, Microsoft has rebranded the company as Xbox Game Studios.
As mentioned, 2018 was a proactive year for Microsoft in terms of Xbox-related acquisitions. The company bought Forza Horizon developer Playground Games. Undead Labs, Ninja Theory, and Compulsion games were purchased in June and confirmed at E3.
Many of Microsoft's Xbox acquisitions continue to operate independently, much like Halo developer 343 Industries. It makes sense to bring all those companies together and Xbox Game Studios seems more fitting.
The rebranding was confirmed by Matt Booty, Corporate Vice President for Xbox Game Studios. In a blog post, Booty says the name fits the elevation of Xbox as Microsoft's gaming brand:
“At Xbox, we believe when everyone plays, we all win. It's why we're passionate about building a portfolio of games for players across console, PC and mobile. As we've expanded our focus beyond the console, the Xbox brand has also evolved from its original roots. Today, Xbox is our gaming brand across all devices, no matter how or where you want to play, or who you want to play with.”
— Xbox (@Xbox) February 5, 2019
Booty says the division encompasses 343 Industries, The Coalition, Compulsion Games, inXile, The Initiative, Ninja Theory, Mojang, Playground Games, Obsidian, Rare, Undead Labs, Turn 10 Studios, and the Microsoft Global Publishing group.
Expected early titles from Xbox Game Studios include a new Halo game from 343 Industries and maybe a new Fable installment from Playground Games. Crackdown 3 and Gears of War 5 are also anticipated Xbox exclusives.