>>3074499It seems clear to me that the forces of the Imperium - SM, the Guard, the Ecclesiarchal military, the Inquisition, even the local armies and militias - will be pushed to the breaking point, Terra will be again besieged, as the Emperor's light fades, his body weakens as the Golden Throne slowly crumbles, the thirteenth Black Crusade successfully crushes everything in its path, and the Ecclesiarchy turns further against the Space Marines.
That is the critical point, which the 5e BRB claims is "at hand", story-wise. Then, what comes after, that's still something for us to wonder about. I suspect the Emperor will finally die and be reborn as an immaterial god of infinite power, and a new Golden Age of Mankind will begin.
Though the problem with this is "where does the story go on from there"? The forces of Mankind united in a galactic genocide seems a bit... well, frankly, boring. Some sort of uneasy truce with the Tau and Craftworld Eldar, containment of the Necrons and Tyranids, maybe also of the Orks... that seems to make more sense. After all, the Tau and Craftworld Eldar seem to be the same Lawful Neutral / Lawful Good orientation as the Imperium, where Orks and Tyranids (which are impossible to reason with and destroy or consume anything for the lulz of it) are Chaotic Neutral / Chaotic Evil and the Necrons are Lawful Evil. I'm assuming that in a post-Star Child galaxy, the legions of Chaos will melt away, becoming mere cults and rogue psykers, seeing as their gods will have been contained by the power of the Emperor Reborn.
Now here's an interesting fluff question. If and when the Emperor dies and is reborn as the Star Child - a transcendant being, a true deity, even The True Deity - will the Space Marines worship it?