Microsoft updated Skype forand 8.1 today, adding a number of new features and improvements. And if you're using the latter OS version, you'll seen some unique additional new features: Cortana and Action Center integration.
All users on Windows Phone 8 and 8.1 will see the following changes:
Increased language support. This latest Skype version dramatically improves language support from 19 to 51 languages. A link to the exact language support list is broken, unfortunately.
Edit last sent message. In response to user feedback, Skype now lets you edit your last sent message.
Improved notifications and fast app resume. Skype push notifications now perform much more quickly than before, and the app resumes more quickly too.
On Windows Phone 8.1, you will see two other changes:
Cortana integration. You can now start Skype calls with Cortana (in the US only). In a video demonstration, Microsoft explains (using surprisingly British people) that you can speak to Cortana, launching Skype with sentences such as "Skype, video call Nick" or "Skype, get Lara Kingwell on the screen." This lets you not just start Skype, but call a certain contact and choose which type of call to make, all in a single phrase.
Action Center integration. Your Skype-based updates now appear in the Action Center.