I can understand the logic behind Surface - to set a standard for PC/RT tablet manufactures and provide a pure Microsoft Windows 8/RT experience. PC manufactures tend to produce a lot of sub-par hardwares with a lot of bloatware and cannot even get drivers right (Apple's bootcamp is way better than what Sony has for Windows 7). The problem is Microsoft has a great software product, but not a great hardware to run it on.
However, these points don't hold for Windows Phone 8. The hardware produced by Nokia is amazing, and there is nearly no bloatware (or can be easily uninstalled without a trace left). The problem on Windows Phone is Microsoft itself - it doesn't help developers (heck, how could you let Bloomberg be a Nokia exclusive?), built-in apps suck (how could you forget to implement EAS security policy securing storage card and how could you not add a timer/stopwatch?), 1st party apps suck (photosync is not available, Skype is so heavily advertised and half-baked beta, PDF reader cannot delete anything, weather app is not supporting the latest features), and finally xbox music/video are disasters. These problems cannot be solved by Microsoft producing its own phones (and Surface Phone owners would lose all Nokia Exclusives).
Of course, Microsoft made some many stupid design decisions in the development of Windows Phone (like not supporting xbox video), therefore, a non-sense surface phone might happen.
However, these points don't hold for Windows Phone 8. The hardware produced by Nokia is amazing, and there is nearly no bloatware (or can be easily uninstalled without a trace left). The problem on Windows Phone is Microsoft itself - it doesn't help developers (heck, how could you let Bloomberg be a Nokia exclusive?), built-in apps suck (how could you forget to implement EAS security policy securing storage card and how could you not add a timer/stopwatch?), 1st party apps suck (photosync is not available, Skype is so heavily advertised and half-baked beta, PDF reader cannot delete anything, weather app is not supporting the latest features), and finally xbox music/video are disasters. These problems cannot be solved by Microsoft producing its own phones (and Surface Phone owners would lose all Nokia Exclusives).
Of course, Microsoft made some many stupid design decisions in the development of Windows Phone (like not supporting xbox video), therefore, a non-sense surface phone might happen.