Microsoft is reportedly now sending out invitations to a launch event taking place in San Francisco.
Google is reportedly extending its Nexus brand to more than one smartphone as part of its promise not to offer preferential treatment to Motorola.
A Microsoft Surface smartphone may be in the works as well, hitting store shelves in the first half of 2013.
Huawei works on its own mobile operating system in case things don't work out with Google or Microsoft.
Microsoft is only previewing the SDK because there are features the company doesn't want to publicly reveal just yet.