A rumor started going around yesterday that said Microsoft would be retiring its 13-year-old Windows Live Messenger client. All Messenger users would be shepherded into Skype so Microsoft could unite its IM clients under one brand. Microsoft wouldn’t comment on rumors yesterday, but it outright confirmed the news today.

On the Skype Big Blog, Tony Bates, President of the Skype Division at Microsoft, announced that all Messenger users who sign into the latest version of Skype with their Microsoft account will be greeted by all their Messenger contacts.

Bates thinks that the move will make things simpler, and improve the overall experience for all users – pre-existing Skype users and Messenger users. To that end, Microsoft will be retiring Messenger around the world at the beginning of 2013. He notes that Messenger will still be available in mainland China.

Bates says that Skype personnel will be on hand over the next few months to make the transition from Messenger to Skype as simple as possible. He also hints that there may be some “special offers,” most likely in the form of free minutes, on offer to those who make the switch.

So what about those who already have a Skype account and a Windows Live Messenger account? When signing in with a Microsoft account, Skype will ask users to merge their accounts. From then on, users will sign into Skype using their Microsoft account.

The move to Skype may be a bummer to some users, but it’s best for Microsoft. Having two IM clients is a redundancy. Moving everybody to Skype lets Microsoft push its far more valuable IM client while delivering more ads to its users.