Lucasfilm has made an official statement:
Here's a recap:
1. The new films will NOT follow any plots from the established post ROTJ EU
2. The movies, The Clone Wars animated series, and the Rebels animated series are the only official canon.
3. EU books, videogames and comics will continue, but continuity will now respect points 1 and 2
4. Existing EU material that does not fight with the scheme above will now be republished under the "Legends" banner, which is similar to Dark Horse Infinity line, or DCs Elseworlds. In other words, they are no longer part of canon, but considered alternate events. Fans are welcome to consider them alternate dimensions, timelines, or whatever else they need to better sleep at night. Popular EU material from this era, like Zahn's trilogy, will continue to be reprinted as long as it is popular.
5. All EU material is up for cherry-picking, but it does not mean the source material is canonized. Meaning, if they add Mara Jade into a future on-screen work, this does not canonize the stories she originated from.
Edited by Driver, 25 April 2014 - 01:08 PM.