ZDNet's Mary Jo Foley reports Cortana won't just be a voice-command feature for Windows Phones, but will be "core to the makeover of the entire "shell" -- the core services and experience -- of the future versions of Windows Phone, Windows and the Xbox One operating systems."
She adds Steve Ballmer has hinted at such a service, talking of a personalized UI that "learns more and more over time about people and the world ... and will be great at responding seamlessly to what people ask for, and even anticipating what they need."
Though Microsoft has some catching up to do against both Siri and Google Now, the company can leverage the huge R&D investments it has made over the years in voice-recognition and AI tech. Of course, Google is also investing heavily in those areas.
Cortana could end up being a negative for Nuance (NUAN -2.4%), whose own R&D efforts have shifted towards natural-language processing and assistant services relative to basic voice recognition. But much depends on how widely it's deployed/adopted.