At this point, the only thing that Microsoft said about their upcoming smartphone is that it is going to be game changing like the Surface but we have not seen and heard anything from them.
The only sign that something might be brewing on the side of Microsoft is the Microsoft Lumia 950 XL. There have been reports of the UK Online store running out of Lumia 950 XL and Lumia 950 and that Microsoft has left it that way for months. Their reluctance to restock the device could be because the device is doing badly or maybe it is because they want to clear up their stock so that they can start bringing in the new model.
Most people believe that Microsoft is holding back the Windows 10 OS update because they want to release it with a new device and there was speculation that it could be the new smartphone or maybe the Pro 5 tablet.
There were also talk about the new smartphone possibly being a Surface Phone. However, that rumor has been going around for some time now so it is best to take it with a pinch of salt until Microsoft announces something.