User blog comment:Shadowunleashed13/New Sonic Boom characters/@comment-34129530-20140723230236

 On May 20, 2014, was informed that Shadow will be part of " Sonic Boom". Though his role still remains unknown in the game and/or TV series.

http://www.tssznews.com/2014/05/20/source-mystery-sonic-boom-character-not-marine-shadow-to-return/