I have asked recently (6/5) via the ScoreCenter app and received this reply:
"Hello ,
Thank you for contacting us.
We apologize for the confusion. We are currently developing a version of WatchESPN for Windows Phone and hope to see it released soon. Please check the Marketplace on occasion as we do not have a firm date for launch at this time.
Regards,
Patrick
ESPN.com Customer Care"
Good to know that it's finally coming to the platform!