According to AllThingsD, Facebook and Skype will soon announce a partnership that will closely integrate the two services. This will be a two-way deal which includes SMS, voice chat, and Facebook Connect. Skype would use Facebook Connect for deep integration into Facebook contacts, while Facebook would offer SMS, voice, and video chat via the Skype service.
This is a natural move for both parties and could also be a big win for users. According to sources close to the situation, Facebook's goal is to bring together communications and community. Rather than build from the ground up, it makes sense for Facebook to look for strong partners in the communications area. This seems to be a running trend in the tech community with Microsoft partnering up with Wordpress and Windows Live Spaces, AOL acquiring TechCrunch, and Google getting it in wherever they possibly can.
Facebook gains a powerful and proven communications system to connect its users and make the service "stickier." Skype possibly becomes the primary mode of communication for over 500 million existing Facebook users. Another benefit comes in stretching across the world. Skype is very popular outside of the US while Facebook is more popular within US borders. By putting their heads together, Skype and Facebook can also bring their users together and increase their global influence.
These updates should come in the 5.0 release of Skype, which is now in beta. It is unknown whether this tight integration will trickle down to the mobile applications and, even if it does, Android users may still be left in the cold by Skype's dealings with Verizon. Skype has also partnered up with other companies as it prepares itself for a public offering.
On a related note, you can still get the Vonage Facebook app, which lets you make VoIP calls to your Facebook contacts around the world for free. It seems to offer the same type of deep integration we might see from a Skype+Facebook deal, but definitely works on iPhone and Android. It doesn't seem that Vonage has any actual partnership with Facebook, though.