It's pretty obvious why Microsoft made the Surface. It needed to raise the bar on Windows 8 tablets and force OEMs into making attractive hardware. It's not a problem with Windows Phone 8 as the Nokia Lumia 920 and Windows Phone 8X are already attractive enough. That might not stop Microsoft from making its own Windows Phone though.
A report from the Wall Street Journal says that Microsoft is working with its Asian suppliers to test its own Windows Phone 8 hardware. It looks like Microsoft isn't fully committed to pushing its own hardware to market though. The product is only in the testing phase for now, and it might never come to market.
Even so, a supplier revealed that Microsoft's phone would feature a display that's anywhere between four and five inches in size. My bet would be on a larger display as Microsoft pushes its Live Tiles as being the key selling point for Windows Phone 8.
It's important to note that all of this is rumor for now, but it's not completely out of the question. Microsoft has only to gain by pushing its own mobile hardware to market. The Wall Street Journal says that even Nokia's CEO, Stephen Elop, would welcome a Windows Phone from Microsoft as it would stimulate sales of all Windows Phone 8 devices.
Even if Microsoft doesn't have its Windows Phone device, carriers will be launching the new line of Windows Phone 8 devices later this month. AT&T, T-Mobile and Verizon will be carrying the impressive Windows Phone 8X from HTC. AT&T is getting the similarly impressive Nokia Lumia 920. The popularity of these devices will surely influence Microsoft's decision on releasing its own hardware.