Re: the Star Wars Expanded universe
The majority of pre ROTJ novels will probably be OK, but most of the later stuff will be trashed. If they're clever they could 'pull a JJ' and wrap up the last novel with an almighty reset to the death of the Emperor and soft boot the whole thing whilst leaving the dumped continuity as another timeline/loop.
Doubt they will bother though.
Soon oh soon the light, Pass within and soothe this endless night, And wait here for you, Our reason to be here...