Will EC adjust it's lore to changes in the evolving narrative and lore expansion that 40K is undergoing (with Gathering Storm) (...)

(...) or will you instead stay focused on the original Arkhona timeline?

The original Arkhona narrative still has a lot of content to get through. The evolving 40K narrative is as much of a secret to us as it is to anybody. We will react to anything major if necessary.