I believe neither that there is a hereafter nor that, if there were one, writers would simply continue their careers as if still alive! As CS Lewis would have said, Heaven (if it exists, of course) is experience of reality, not continued writing, or other artistic representation, about reality.
Decades ago, the travel writer, Peter Fleming, was contacted by a man whose young daughter practiced automatic writing and had purportedly produced a new James Blond novel really written by Peter's deceased brother, Ian. Peter Fleming concluded that the man and his daughter were honest and that she really did write books automatically but that this text could not possibly have been authored by his brother unless the hereafter had a very bad effect on an author's style and creativity.
If there are to be any further Technic History or James Bond novels, then they are going to have to be written by authors who are still alive but can any one writer satisfactorily reproduce the style of another?
According to Michael Ward in Planet Narnia, there are seven and only seven Chronicles of Narnia, because CS Lewis based each book on one of the seven planets of medieval astrology/astronomy. Someone might add intermediate volumes about, e.g., what Peter was doing back in Narnia while the others were in Calormene, but it would have to be someone who either shared or at least fully empathized with Lewis' distinctive brand of Platonic Christianity. Difficult.
We compare Anderson favourably with Fleming and Lewis, different though they are - to say the least! Imagine an encounter between Axor and Aslan.