User blog comment:ImperialFist31/42nd Millenium/@comment-26233146-20150323084856

There are some scattered stories that are implied to take place in the 42nd millennium like the Priests of Mars series and the second Dawn of War game if that's what you're after.

As for why they don't advance the storyline, it's simple, they've set up this massive galaxy with several things about to happen that will change the whole galaxy (Ynnead is about to be born, the Orks are unifying, the Golden Throne is breaking and the Tyranids are about to arrive to name the big ones), these changes will alienate a lot of people if they happen (imagine how many Eldar fans would be upset if Ynnead was unable to kill Slaanesh when it is finally born or how many Chaos fans would be upset if Ynnead was born and permanently killed Slaanesh for example). Games Workshop figures that just basing codexes around the time when things are about to happen will allow them to keep making money without alienating too many people. -The Bloody Raven