take place about 30 years after the end of Return of the Jedi and two, that principle photography will begin in May 2014. As for who is cast, so far only R2-D2 is confirmed but it will "will star a trio of young leads along with some very familiar faces." The trio of young leads probably being the offspring of Luke & unknown and Han and Leia who will also be in the next trilogy of films in some form or fashion. So far the casting rumors for that trio has all been late teens to early 20s with names like Lupita Nyong, Jesse Plemons and others being named dropped.
For the geeks, the proper phrase for the time jump would be 34 ABY which means 34 years After the Battle of Yavin when the first Death Star was destroyed in Star Wars: Episode IV A New Hope. Anything before that "year" is measured as BBY (Before Battle of Yavin). At 34 ABY, technically the Expanded Universe (EU) could remain intact as that would set the movie after the Yuuzhan Vong invasion that destroyed multiple planets, decimated the Jedi corps, killed one of the Solo children (and Chewbacca) and also lead to severely weakening the Republic formed after the Empire fell in Return. Only problem is Ben Skywalker had not been born and the other two Solo children were in mid-teens. Still wish had gone with 42 ABY as the novels had set it up so that the fully re-consituted Jedi no longer trusted the Republic (and vice versa) while a planet full of Sith begin to conquer the known universe. Seems that is more ripe for epic storytelling while keeping intact all that came before.
Really though this is just for giggles speculation as we are talking JJ Abrams. He has zero knowledge or interest in the EU. At some point he probably googled "Star Wars Expanded Universe" so he at least understands the question when asked about it but his knowledge is limited to whatever he skimmed on the page. Sad for long time fans who enjoyed the franchise beyond the six movies or cartoons and a big eye roll for those that only know about Star Wars from the movies and cartoons. With news of a start date, maybe we might actually learn who is cast but if Star Trek was any indication (it took set leaks just to learn character names), it might be a while before who what their roles are much less the story itself.