The bare bones of quite a lot of Robert Louis Stevenson potential work did not die with him, because he had told the outline of what he was about to write (actually, he dictated) to his amanuensis. From those outlines, Sir Arthur Quiller-Couch was able to finish "Ivanhoe".

It would be a favour to all of us if Terry would record or tell others of as many outlines as possible, so that his family and/or literary agents could select writers to fill in the outlines later. It would provide an ongoing additional revenue stream for his family too.

It would not be all that different from what Ursula le Guin seems to have done in later life, when she produced a large number of books with dual author credits with a range of other writers - and to my eyes at least the writing differs so much that I suspect that the co-authors did most of the actual writing.