During a demonstration at the Build 2018 conference today (May 7), Microsoft and Amazon showcased how Cortana and Alexa could be opened on the same smart speakers.
Cortana to be rolled out of most of Microsoft services, especially Office 365. Nadella says they are building a version of Cortana that can talk to other AIs. Microsoft is working with Amazon to make Cortana work with Alexa digital assistant.
Alexa will work on Windows 10 too, with Cortana. You can call Alexa as you do cortana.
Microsoft and Amazon eventually hope the partnership will herald an era where both assistants will work in tandem, with the best equipped to answer a specific query taking the lead.