From what I've read, it looks like Fox will be retaining the distribution rights to the existing Star Wars films--Disney will only have rights over the new films. It's also important to note that although Disney has indeed purchased Lucasfilm, it will not be absorbing and/or merging with it; rather (for the time being, at least) Lucasfilm will be operated as a subsidiary and will be headed by Kathleen Kennedy (which isn't quite so bad). Lucasfilm staffing will probably remain relatively unchanged.