Please remember that until we get an official announcement, even this is considered to be rumor.
I would imagine that a digital version as well being released at the same time. No idea of what the companion guide will be, but getting a full hardcover release is a very big deal. We might very well be seeing what 40k radio was predicting with their rumors of a 3 army codex.
Imperial Knight Titan: 1 kit will make all the versions.
Imperial Knight Titan Codex: Three armies in this book.
1st Army: Imperial Knights Army
2nd Army: Mechanicum Army
3rd Army: Freeblades Army (Mercs that can ally)
With Sentinels of Terra, Legion of the Damned, Tyranid Dataslate II, and the Imperial Knight model all being released this weekend, you had best save up some of that cash for the codex.
So here is what we are seeing for the 1st week of March.
Codex Imperial Knights: $41
Codex Imperial Knights Companion Guide: $74.25
Codex Imperial Knights Limited Edition: $115