From his Facebook page:

2012 Convention Announcement – Here's a preliminary list of cons that James is scheduled to attend in 2012: New Orleans (January 28-29), Calgary (April 27-29), Philadelphia (June 1-3), Chicago (August 9-12). Check the "Events" tab for more information on individual cons. More convention announcements to come!

http://www.facebook.com/JamesMarstersLive?sk=events