Usually it boils down to obtaining the source material. If you haven't checked book prices lately, GW stuff isn't always the cheapest. Once the source material is acquired then when can get going post-haste on adding new content. Since we only have a few full-time, dedicated editors that post the majority of the content, this can take some time, as many of these editors are already tasked with a myriad of projects. If you happen to acquire the source material yourself, by all means...please make a new article and share with the rest of us!
Please be patient with us, as we attempt to update the wiki. Thanks for your understanding!
P.S. Check out the [warhammer40k.wikia.com/wiki/13th_Black_Crusade] article. A lot of new info was added from the first Gathering Storm book.
Greetings oh wise one...
Trust me, GW will milk the HH Series for as long as they can.