User blog comment:Cpt. Riley/Infinity Ward Co-Developing MW3 w/ Sledgehammer/@comment-78.145.38.84-20110123133411/@comment-78.1.130.21-20110123141137

It actually is going to be a prequel (according to this source: http://callofduty.wikia.com/wiki/User_blog:N7/Modern_Warfare_3_could_be_a_prequel )