Starting January 2018 Microsoft will the option to sign in to Skype using your Facebook account. Facebook login will be disabled because Microsoft is rolling out a new Skype experience for desktop and mobile platforms.
Therefore, Skype users will now have to use the existing Microsoft account or create a new one in order to continue using the Skype service.
Skype customers will also be able to transfer their Skype Credit, Number and subscription balance from the Facebook account they were previously using. Detailed steps on how to transfer your Facebook account data can be found HERE.
Microsoft has also provided a tool for transferring your Skype Credit and Subscriptions from your Facebook account to your existing or new Microsoft account which can be found HERE.
Here is the official announcement from Microsoft:
As we continue to roll out the new Skype, we’re discontinuing the option to login via Facebook in January 2018 and will streamline all Skype logins via your Microsoft account. Using a Microsoft Account will enable you to login-in via single sign-in, unlocking all your Microsoft services – including Skype, Office Online, Outlook, OneNote, OneDrive, and more – in one experience, with just one password. Currently, using your Facebook account to sign in to Skype is not supported on Skype for Windows 10, the new Skype for Android and iPhone, and the new Skype for Windows, Mac, and Linux.