Well its based on my experience with Total War: Empire, Napoleon and Shogun 2... you can also toss in Sega's management of the AvP3 IP.
The CA games all launched buggy as hell and required patching to get to a working state, especially performance... Shogun 2 had its much vaunted Dx11 feature patched in ages after launch, and each of the Total War titles had DLC units in spades... and Shogun 2 had a gore DLC that added blood effects.
AvP3 developed by Rebellion and published by Sega, launched buggy, and DLC came before the first patch... the promised dedicated server tools came ages after launch.
I believe the issue is to do with Sega, and them aggressively pushing dates even if the product is not ready... they tend to prioritise the accountants opinion over the developers.... hence my aphrehension.
I cant see CA making a brand new engine for the Warhammer game so I believe they will merely mod the most up to date version of thier TW engine... and the AI for all the TW games was always the worst part of the games, not many dispute that opinion.