Maybe I'm the only one, but I predict a good $50 million hole in the THQ books by the end of the fiscal quarter in which this is released.
Firstly, and most importantly, the 40K universe is not a place where the actions of a single person can make that big of a difference. With the exception of the Inquisition, how often do you hear about single, mortal beings making that big of an impact? You don't. What you DO hear about is massive armies fighting other equally massive armies in meat grinder military actions that take generations to resolve.
Secondly, the 40K universe is all about the idea that anyone can die at any movement for any reason. Being a perpetually regenerating immortal guardsman kinda destroys the whole concept.
Finally, WAR's faceplant out of the gate has already shown us that there isn't a big enough built in Games Workshop audience to support a whole new MMO. And yes, I know there are more 40K players in the US than Fantasy, but they have all spent countless money and man hours putting together, painting, and playing with personalized armies, do you REALLY think they are going to want to invest all over again in who new genre of entertainment?
My prediction, people will play it, but it won't carve out anywhere near the nitch that THQ is hoping it will.