Update: It seems like I am close to the mark. Take a look at the Daemonblade entry in the above image. Word for word from Codex: Grey Knights. This is looking more like a word-for-word translation from the Grey Knights rather than a true update.
This post is strictly for my own amusement as I attempt some prognostication regarding Codex: Inquisition based on the recent spate of supplement releases. I know nothing about the actual contents of the book.
Warlord traits - new d6 table
Wargear - same as C:GK minus grey knight specifics
HQ - Inquisitors (new/old named and generic) same ordo split and wargear options from C:GK
Elite - Assassins from C:GK
Troops - Henchmen with same options from C:GK
Dedicated transports - chimera, rhino, and land raider (LR possible Inquisitor only)
Fast - Storm Raven (C:GK version)
Heavy - Land raider
And that's it... I realize that this looks like a fairly cynical view but this would allow someone to field an entirely Inquisition force if that is the desire. There will be some new background and perhaps more named inquisitors but no new units and I would be surprised in they brought back stormtroopers as a standalone troop choice (these are easily represented with current henchman options).
I would like to see a return to the flavor of the Lord Inquisitors of the Daemon Hunters book along with unique psychic powers, artifacts, funky new retinue options, etc. Honestly, I even find the rumors of plastic stormtroopers to be wholly far fetched. The current rumor sounds like a far-to-complete listing of sprue bits from a guy who supposedly only got a quick look at the models. Sounds more like wish listing to my ears.
Alright enough Debbie downer stuff. Like I said, this post is for my own amusement and only useful as a way to see if I managed to roll up an accurate Divination power for this release!