A multiplayer beta is scheduled to start in Summer 2010, with invitations tied to another of Ubisoft's freshened franchises, Splinter Cell: Conviction (which is but a stone's throw away from release). The offer is currently extended only to the Xbox 360 version of Conviction -- and aside from Microsoft's system, no platforms have been explicitly mentioned in Future Soldier's announcement. He's from the future, so Facebook is a likely candidate.
Update: According to one of Ubisoft's Twitter accounts, the "same experience, same development team and same release date" will be coming to PlayStation 3. Ubisoft's Kimi Matsuzaki also noted that PC details would come "later."