The Facebook Messenger app for the iPhone lacks a video chat function and It seems Facebook is looking to remedy that with Skype video chat integration. It's also possible that the update will include other improvements, and the earliest the update will hit iPhones is a rumored June 2012.
And while Facebook has concentrated on having dedicated Facebook Messenger apps for the iPhone and Android Phones,the iPad has not seen a dedicated Messenger app. All of that is set to change though as a source has revealed to 9to5Mac that a standalone Facebook Messenger app is planned for the iPad. The application is a larger version of its iPhone sibling, and will sport functions similar to the iPhone version. One-to-one messaging, group chatting and push notifications will be available to the iPad version, making it more convenient for users to chat instead of accessing the Facebook app just to chat with friends.