Well, apparently the studio isn't too happy with second rate femme talent, and recognizing that Cuaron's CGI heavy film will need a major A-list star to put butts into seats, they recently went back to her a second time. Again, she gave them the cold shoulder. Jolie's busy prepping her directorial debut so she hasn't got the time.
A script review of Gravity was released, and it shows why the studio might be reluctant to hire marginal actresses like ScoJo or Lively. The main role of Ryan, the woman trapped out in space after a satellite crash kills everyone aboard her ship, demands that the actress be on screen alone completely by herself for the bulk of the film. While that worked pretty well last year for Sam Rockwell in the similarly themed Moon
This is a Cuaron flick, so you know no corners are going to be cut by the director. It's a huge, sprawling project(the opening scene is rumored to be 20 minutes of a single shot) that's going to cost a lot of money. But it also doesn't appear to be an action movie, so having a bankable actress is paramount. Without it, I don't expect it to ever get off the ground. Let's hope that's not the case.