I think one of Microsoft's problems is they only invest in cutting edge technologies that others are already working on, coupled with the fact that their competitors execute better. They seem to have forgotten what it's like to be a startup and throw everything you've got into a new product. Maybe they've grown too conservative, afraid of risk, but it's hard to innovate without risk.
Cortana will die soon because MS has killed Windows Phone. I really do not know why MS did not want a mobile system for the business segment. It not have to be cheap at all. It did not have to have 100 million games in the store. The business user does not expect this from the phone. Safe way of logging in (e.g. with a finger-tip), durable construction, PureView 16 Mpx camera (or maybe a newer version of this from Lumia 1020). Excellent support for video conversations (SKYPE and other solutions). For this very capacious battery and very economical mode of operation (minimum 1 week in the majority of services excluded). Laser pointer (for presentations), IR transmitter (for beemers). Thats most for modern business phone.