The release of the Skitarii Vanguard boxset is here, and in the description of the Vanguard it specifically mentions Codex Skitarii. There has been a lot of emails coming into my inbox saying that there wont be a Skitarii Codex, due to the models being under an Adeptus Mechanicus tab. So I just wanted to be clear that we have seen mention from Games Workshop that there is a Codex: Skitarii coming.
Here is what the text says. I had put this in bold yesterday when the models were released, but I did not mention it.
via Games Workshop in the Description of their new box set.
This bundle contains everything you need to make ten Skitarii Vanguard and ten Skitarii Rangers, including two optional Alphas. 248 components are included in total, with forty-six heads, fifty weapons (enough to make any combination allowed for in Codex: Skitarii), a 210mm x 297mm Mars Skitarii Transfer Sheet, a pot of Martian Ironearth Technical paint and twenty 25mm bases.