New to 40k/BT. Are we getting a new army rule?

Title. Coming over from AoS for a bit. Just starting my collection with the Armageddon box, waiting on the space marine codex before getting anything else. It seems like we are getting new stats for the units, so we should expect some kind of separate free PDF? Are they likely to issue more codex supplements(like the 10th BT) later on?