"This product will also be available as a range item, replacing the existing Age of Darkness box set."

So there's no need to pre-order the moment it comes up for sale, then?
I can just buy it whenever?

Någon som vill dela på Saturnine-lådan med mig?

They're rolling out everything all at once.

https://www.warhammer-community.com/en-gb/articles/zojna4pr/sunday-preview-the-horus-heresy-begins-with-saturnine/