SW EU is mostly straight, no parallel universe.
Actually, the ExU is mostly considered a parallel universe that sticks to the films as much as possible. I call it an overlapping universe, since George has used ExU material in the movies. Episodes I - VI are their own self-contained Universe. The George or G-Canon universe. Then there is the Films + Expanded Universe reality that most of us know. It takes George's story and expands on it both prior to and after the movies themselves. With the new Episode VII, IF it is in fact an original story that would retcon the majority of the post-RotJ ExU, it would fall into a different category. G-Canon is done, as far as the movies go. Since George is not going to have his name on VII except on the "Star Wars Created by George Lucas" credit, it won't actually BE G-Canon. I'm calling the new Disney franchise D-Canon for now, and IF the rumors are true and it differs from everything post-RotJ, it would cause an all new Universe. Right now, we have the OT/PT/ExU. WIth the new movies, we'll have the OT/PT/Disney Universe as well. It's a compromise, but it's the most likely option to keep the ExU fans from going completely ballistic.