Updated News. It seems that there will be a bonus disc with each trilogy.
So there will only be one exclusive Bonus Disc with the Complete Saga boxset...
The following news comes from a Norwegian home cinema publication which interviewed Vincent Marcais, Senior Vice President Marketing at Twentieth Century Fox International in Europe.
Star Wars: Original Trilogy and Star Wars: Prequel Trilogy will consist of four discs each. One for each movie and one bonus disc. Star Wars: The Complete Saga will have an additional special features disc, for a total of nine.
The remastering of the movies has been performed by Lucasfilm and will offer "the most recently updated versions of the movies," with "even more enhancements to the picture quality." When asked about Fox's answer to the fans that want to see the three original versions released, Marcais replied: "The versions that are being released are closest to George Lucas' vision. Other than that, no comment."
There is currently no date for a Blu-ray release of the six Star Wars movies separately.
Sales expectations are very high. For reference, the Avatar Blu-ray sold 5 million copies in the US and 4 million in the rest of the world. That's the "ceiling" on what sales to expect from a major Blu-ray release, and Star Wars is expected to raise that ceiling.