NokiaWP.net and while not too much is known about the device, the thickness of the handset and the horizontal line that slices the device in two suggests that it is a side-sliding QWERTY keyboard model. Sony (Ericsson) has said it would not develop any handsets using Microsoft's mobile OS after deciding to go with Android and it is possible that we are merely looking at pictures of the canceled "Julie" handset prototype.
On the other hand, NokiaWP.net says that the phone in the picture is running Windows Phone 7.5 which would indicate that some recent work is being done with the unit and with MWC coming up next month in Barcelona, perhaps "Daughter of Julie" may be making the trip. And if you are confused by the Sony Ericsson name on the device, remember that Sony plans on dropping the "E" word from its phones and we already have the first two Sony-only phones: the ion and the Xperia S.
source: NokiaWP.net via WPCentral