Prince Xizor and the Black Sun would make a terrific villain and organization for Luke, Leia and the former Rebels to fight in the new Sequel Trilogy but, alas, book canon dating back to the mid-nineties places Xizor's defeat and death before JEDI (circa 4 ABY) and he and Black Sun can't be used unless the Shadows of the Empire storyline is decanonized and dumped so they can be used in the future films. SOTE is a pretty beloved and accepted piece of non-filmed SW lore and I doubt it would be shelved and forgotten so easily.
By fanboys - if Disney wants to recycle the characters, it will without a second look, the money you spent on those books came in and was spent years ago.