Just because the specific history will be dropped does not mean characters can not be used in new different ways. When Disney bought Marvel they got a huge group of characters. But they have not had adaptations of specific stories.
I would expect some of the 'broad strokes' of the old EU to carry over - Mara Jade being the former Emperors Hand, Dash Rendar being a smuggler, some of the inevitable new Jedi being versions of existing characters etc.
If they try to say any of the following didn't happen: The Thrawn campaign Daala's machinations Ysanne Isard and her revenge The Yuuzhan Vong invasion and war They can go and get fucked in their big mickey mouse arse.
I'd say it's almost guaranteed that ALL of that gets binned. Anything that carries over will probably be as general as 'Mara used to be The Emperors agent', 'Xizor headed the Black Sun criminal empire' or 'Kip Durron becomes a new Jedi'. Nothing more specific, and no old plotlines. They need a clean slate plot wise for the new films. It is utterly inconceivable that movie screenwriters would be constrained by hundreds of (sometimes contradictory) books and comics. The EU has an audience of thousands, the new movies, millions.
I doubt they care enough about some unimportant book stuff to actually say it didn't happen, they'll do whatever they want and if it contradicts the EU and some fanboys start screaming in agony ... well, then nothing because Disney still won't care. The EU is not and never was canon and please, no one start explaining the different levels of Star Wars canon, if something is a "lower level of canon" and the people in charge can ignore and overwrite it by producing actual canon material whenever they want then the lower level was never really canon to begin with. S, F, D etc. canon was just a fancy way to say "non-canon".
They might not give a damn about the old EU, but I'll bet as a marketing tool any new books get branded 'New EU' or something similar. The implications for the old EU are obvious...
If Disney turns the Thrawn trilogy into glorified fanfiction overnight, it will be a kick in the teeth to true SW fans. A real "fuck you" moment. Anyone who doesn't understand that isn't a real SW fan at all.
The Thrawn trilogy has always been glorified fanfiction. I'm not even sure there's anything wrong with that, actually, but it sure ain't Disney's fault.
Oh, please. Don't we get enough of the "true fan" and "real fan" silliness in the endless nuTrek debates? Neither STAR WARS or STAR TREK is intended ONLY for the hardcore fans--and nobody in their right minds makes a $200 million movie ONLY for the folks who have read every comic book and tie-in novel. STAR WARS belongs to everybody. The books and comics can be a lot of fun, but forcing the actual movies to stick to them would be like the tail wagging the dog . . . .
I think it's pretty safe to assume that the Thrawn trilogy will bite it because it would roughly be in the same timeframe as the new movies if they take account the age of the original actors and set the movies some decades in the future. The only exception would be if they use Thrawn as the new main villain which i would be all for as he's an awesome character (the trilogy less so.. too much of "Heroes at the right place and right time to thwart the villain" syndrome). I fully expect the EU to get disregarded for the most part except for maybe the most recognizable new characters like Mara Jade and such, at best they'll use established characters and just write new stories.
http://clubjade.net/?p=48855#more-48855 An interesting article from Clubjade, about the future of Star Wars
Thrawn could actually be safe because of the actors ages. Jedi was released 30 years ago. If they jump the movies 30 years that would put it in the New Jedi Order. Now i doubt Disney will care about the new republic books, and it will most likely create a brand new story, but adding the original actors only helps to skip over Thrawn and that era.