Microsoft initially planned to shut down Windows Live Messenger on March 15 and migrate all the users to Skype. Now the company has announced that on April 8th, Microsoft will start blocking the existing users out of WLM. Users will have to upgrade to Skype where their contacts will remain intact. If you've already migrated to Skype and, have lost your Messenger contacts then refer this link to restore your contacts.
The process will take a few weeks to complete. English-speaking countries will be the first to be forced to move to Skype, while the transition will officially end on April 30 with Portuguese users.
Please note that Messenger Service will not be ceased. You can use third-party clients such as Pidgin, Adium, Digsby, and Trillian to chat with your Messenger contacts after April 8th.