Fans have often assumed that any sequel films would be built around the events in the Expanded Universe, but that has all just been rumor. Absolutely nothing has been put out there that indicates that that is the case. In fact, it would be safe to say that it's doubtful the plot will follow the same path, as the Star Wars Expanded Universe series was not directly controlled by George Lucas himself.
That being said, elements from the Expanded Universe have popped up in other films in the past, so it is not beyond the realm of possibility that things can take shape from a familiar source. Coruscant has its origins in the Expanded Universe but was incorporated into Star Wars: Episode I - The Phantom Menace and actually became one of the principal aspects of the prequel trilogy. Countless other things have made their way into true canon or had an influence on the films, whether they were important (like the Hutts being an actual race) or somewhat meaningless fun (such as the inclusion of Jedi Master Quinlan Vos in Star Wars: Episode III - Revenge of the Sith).
Until now, the fans have been kept in the dark about the new films and their relationship with the Expanded Universe material. However, Lucasfilm has finally shed some light upon the situation:
For over 35 years, the Expanded Universe has enriched the Star Wars experience for fans seeking to continue the adventure beyond what is seen on the screen. When he created Star Wars, George Lucas built a universe that sparked the imagination, and inspired others to create. He opened up that universe to be a creative space for other people to tell their own tales. This became the Expanded Universe, or EU, of comics, novels, videogames, and more.Translation: we could very well see anything brought into these new films that previously existed in the Expanded Universe—but it may not be exactly the way that it was before. Perhaps the Yuuzhan Vong are the enemies but don't have the same appearance or resistance to The Force. Maybe instead of having twins, Leia and Han Solo only had Jacen, and maybe nobody has turned against the Jedi Order. Maybe Ben Skywalker isn't the name of Luke's son. It's doubtful that we will see any clones of Emperor Palpatine, but we could see a Jedi Knight like Kyle Katarn amongst the cast.
While Lucasfilm always strived to keep the stories created for the EU consistent with our film and television content as well as internally consistent, Lucas always made it clear that he was not beholden to the EU. He set the films he created as the canon. This includes the six Star Wars episodes, and the many hours of content he developed and produced in Star Wars: The Clone Wars. These stories are the immovable objects of Star Wars history, the characters and events to which all other tales must align.
Now, with an exciting future filled with new cinematic installments of Star Wars, all aspects of Star Wars storytelling moving forward will be connected. Under Lucasfilm President Kathleen Kennedy's direction, the company for the first time ever has formed a story group to oversee and coordinate all Star Wars creative development.
"We have an unprecedented slate of new Star Wars entertainment on the horizon," said Kennedy. "We're set to bring Star Wars back to the big screen, and continue the adventure through games, books, comics, and new formats that are just emerging. This future of interconnected storytelling will allow fans to explore this galaxy in deeper ways than ever before."
In order to give maximum creative freedom to the filmmakers and also preserve an element of surprise and discovery for the audience, Star Wars Episodes VII-IX will not tell the same story told in the post-Return of the Jedi Expanded Universe. While the universe that readers knew is changing, it is not being discarded. Creators of new Star Wars entertainment have full access to the rich content of the Expanded Universe. For example, elements of the EU are included in Star Wars Rebels. The Inquisitor, the Imperial Security Bureau, and Sienar Fleet Systems are story elements in the new animated series, and all these ideas find their origins in roleplaying game material published in the 1980s.
Demand for past tales of the Expanded Universe will keep them in print, presented under the new Legends banner.
On the screen, the first new canon to appear will be Star Wars Rebels. In print, the first new books to come from this creative collaboration include novels from Del Rey Books. First to be announced, John Jackson Miller is writing a novel that precedes the events of Star Wars Rebels and offers insight into a key character's backstory, with input directly from executive producers Dave Filoni, Simon Kinberg, and Greg Weisman.
And this is just the beginning of a creatively aligned program of Star Wars storytelling created by the collaboration of incredibly talented people united by their love of that galaxy far, far away...
Basically, we have more answers than before, but still no real answers. It appears as though we're in a for a long haul before anything concrete is released about Star Wars: Episode 7. The Fanboy in me is just going to have to grit his teeth and cross his fingers for a little while longer and hope that things don't go the wrong way.