Microsoft’s intention to bring full mouse and keyboard support to Xbox One is beginning to materialize: Minecraft Beta on the Xbox Insider Program now features an option to use the former, although the input lag is reportedly bad enough to be noticeable.
Microsoft has stressed that they have no plans to allow mouse support where it doesn’t make sense, such as forcing controller players to compete against mouse players in competitive FPS or RTS. It does seem as though Minecraft has the ability to enable and disable mouse support at will, given the fact it can be toggled in the menu for Minecraft. This indicates that you could see scenarios where there are mouse and keyboard playlists, and controller exclusive playlists, to prevent anti-competitive behavior.
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Source: [H]ardOCP – Xbox One Mouse Support Finally Arrives for Xbox Insiders