Not so much a nail in the coffin, but a kick to the side.
The current "established" (I use established as loosely as I can) post ROTJ cannon is just not a matter of cannon anymore. It is now just a different set of stories. Like how in Marvel you have the Age of Apocalypse timeline, and the Days of the Futures Past timeline, and The Ultimate universe. It doesn't remove those books from existence, it just makes them their own "timeline".
That's probably the best path to take. Have the movies and novels take place in seperate timelines, but the novels still following the same trend as the movies. That's kind of what has been happening before all of this, but now the novels will have less room to work with, imo.