New Information regarding the Cult Mechanicus is here. There has been lots of rumors regarding the models that will be in this codex, whether it will incorportate Forgeworld, if the Skitarii will be a part of it and so on. Today we have some very solid answers.
Please remember that these are rumors, and from a very credible source.
via an anonymous source on Faeit 212
Cult Mechanicus codex is coming, but I do not have a release date. What I do know is that it is 80pgs long, and is not a full codex like SM, Eldar, etc. Instead its similar in size and unit count to the Skitarii codex. and no, the Skitarii and Forgeworld Mechanicus are not part of this codex. Their allies are same as the armies of the imperium.