I don't think they will come out with a Mobile device anytime soon, or maybe even at all. As we know, they completely killed off what was left of W10M and for the few of us who still rock their Microsoft phones this is our last year with any support from MS. Their best bet is to create a new category, just like they did with the Surface line. Andromeda is rumored to come out, but that is more of a pocket computer, a companion to your phone, not so much a phone replacement. MS best bet for an actual Mobile looks to be resting on its partners. The only questions here is whether MS is trying to develop an OS that is both part of the Windows ecosystem and can be used as a mobile OS. Two big issues I see with this is 1) App gap; they need to get the developers to bring some of the big name apps to the platform and 2) The bitter after taste of what W10M could have been and that is still fresh in the ones of most of us. An aggressive ad camping showing of its capabilities and how it stand out from the rest, and at the same time integrates to an already robust ecosystem would be the solution for
#2 . The big one tho is the app gap. Only time will tell if MS themselves will actually try (again) to bring a mobile option to the world. Although I highly doubt that