Whether or not Sony Mobile Communications (previously Sony-Ericsson) will commit to a Windows Phone has been a back and forth for some time now. They dipped their toe into the ecosystem back on 2010 with the "Julie" prototype which was then canceled and since then, have been open but not committed to the platform.
A recent rumor suggested that they would make a device but not till late 2012 i.e. when Windows Phone 8 "Apollo" hits--a reasonable decision in our mind. However, Phone Arena, in a meeting with Sony Mobile Communications during Mobile World Congress, managed to get a little more info from the company and it doesn't sound too positive on the prospects.
While Sony are still "open" to the idea evidently they're not too keen on it either. If you wonder "why not" Sony's answer is "Because no one really cares about WP".
Harsh words from a company struggling to turn a profit in 2011 and 2012 (they're down 20% in shipments from a year ago and lost 247m Euros, according to the BBC). While they will still push forward with Android, the prospects for a Windows Phone from them still seems slim, at least for the near future.
Of course in a mobile world dominated by Samsung, HTC, Nokia and Apple, one has to ask: Does anyone care about Sony anymore?