Microsoft has just announced that they will be retiring several Skype apps in about a month’s time (July 1st). The affected platforms are Windows Phone 8, Windows Phone 8.1, Messaging for Windows 10 Mobile, Windows RT, and Skype apps for TV. It’s important to note that Skype for Windows Phone still works, although it requires the Windows 10 Mobile Anniversary Update or later. This was originally announced last year, but no date was given at the time (just "in the coming months").
Some sites are noting a workaround for affected users: Skype for Web. Unfortunately, this is probably not a viable option in most circumstances. Specifically, Skype for Web does not officially support mobile browsers, which means that Windows RT users might be in luck, but every other affected device is without options come July 1st.