UPDATE:  Just announced! Samuel L. Jackson (Nick Fury) joins Tom Hiddleston (Loki), Clark Gregg (Agent Coulson), and Director Joss Whedon in our Global Fan Chat today! Assemble at 2 p.m. ET/11 a.m. PT!    Marvel Studios announced today that they will be sponsoring a Global Twitter Chat on Tuesday, January 31, 2012 at…