As with many chat applications, group chat is usually an integrated feature. Now that Facebook is integrating video chat features like that of Skype from SocialEyes, it makes more sense to add the same group chat features.
Facebook purchased iOS Beluga, a group messaging service, of which they now have control over the application and dev team. There aren't too many details in regards to the group chatting feature about when we'll be able to see it, but perhaps sooner than we think.
With all the new features Facebook is integrating with its messaging system, it seems that it will soon become the ultimate social platform for keeping in touch with friends and family.
Since Facebook is adding these social features to better the communication amongst friends, they should really work on their mobile app. It's already on top as far as connecting with others and sharing within the web next to Twitter. Hopefully they'll come out with a better app that supports if not all, but the majority of the features it claims to be getting.