Is Skype for Windows Phone 7 discontinued?
Yes. We want everyone to experience the best Skype has to offer – from enhanced quality to better reliability to improved security – and the newest version of Skype is the way to do that. So everyone can benefit from the latest improvements, we sometimes retire older versions of Skype across all platforms, including mobile devices. For that reason, we have permanently retired all Skype apps for Windows Phone 7.
As a result, you can no longer be able to sign in and use Skype on any Windows Phone 7 device. You can still use Skype on a variety of mobile platforms, including Windows Phone 8 or 8.1, but unfortunately, Skype is no longer available in any form on Windows Phone 7.