According to Deadline Lucasfilm (now owned by Disney) have decided not to go ahead with any more re-releases of the Star Wars prequels. Star Wars Episode II: Attack Of The Clones was to hit screens in 3D on September 20th, 2013 and Star Wars Episode III: Revenge Of The Sith was to open in 3D on October 11, 2013, but neither will go ahead.
The reason given is that Disney wants to focus only on “rebooting the franchise”, but it could have something to do with The Phantom Menace making less than $45 million worldwide when it was re-released February 2012. There was obviously an interest there from fans, but not a big enough one warrant further 3D outings.
Star Wars Episode VII will be directed by J.J. Abrams and is scheduled to be released in 2015, but it could be pushed back depending on when filming begins. Abrams will no doubt want to get the story in tip top shape before moving forward given the expectation on his shoulders.
Update: Official word from StarWars.com:
Lucasfilm has decided to postpone this fall’s scheduled release of Star Wars Episodes II and III in 3D. Given the recent development that we are moving forward with a new Star Wars trilogy, we will now focus 100 percent of our efforts on Star Wars: Episode VII in order to ensure the best possible experience for our fans. We will post further information about our 3D release plans at a later date.