Golden Sun 3 Speculation
There has been some speculation that Golden Sun 3 will be taken on a project by the company owned of Camelot for a new generation console (such as DS or Wii). Although, we can assume that if it were created that since Alex, Saturos, Menardi, Karst, or Agatio are no longer in the world, they will not be an antagonist. However, some may argue that the fate of Karst and Agatio are not yet confirmed, since Camelot seems to have been too lazy to put them on the map they were seen almost out of energy if you returned to it. It is possible that the two survived long enough to be recharged from the lighting of Mars Lighthouse.
 Fake Games
There have been two games that are fake created too look like Golden Sun 3. Both of which are for the DS.
One of them is called Golden Sun: Alex's Road, and the other is called Golden Sun: The Golden Soothsayer. However, many people have created fake boxart for Goden Sun 3, but none of them seemed to stir up as much chaos as the other two.
 Golden Sun DS
However, it seems like Golden Sun 3 will be released for the DS as Golden Sun DS, which could possibly make all of the above irrelevant.