The Italian site iphone italia claims that a future update of Facebook Messenger video calls over Skype will add. This would be familiar with the developments at Facebook have told. The app is currently in use to exchange messages with other Facebook users, such as with WhatsApp and iMessage possible.
The sources for iphone italia also showed two screenshots of Facebook Messenger update. Really dressed the app still does not matter: there are only a few buttons to answer calls, reject and end with a big rectangle where video is displayed. The images are real, then we suspect that the design of the app still needs to be refined.
Very unlikely the video would not be added within the app. Currently Facebook is working closely with Skype, making it all possible with visitors from Facebook via a computer video calls.