GWJ Conference Call Episode 76 on Gamers With Jobs promises hints about plans for a Sins of a Solar Empire expansion as part of their conversation with Ironclads' Blair Fraser about the PC RTS game. I can't access the podcast myself, but maybe you can, and if not, we can take comfort in knowing an expansion is in the works. On a semi-related note, the Sins of a Solar Empire Website has news on upcoming two patches, saying their current plan is for a version 1.04 patch, which "will contain some balancing updates based on player feedback, more computer AI updates, and other game play tweaking." This will be followed by a version 1.1 patch described like this:

This will be a more significant update providing a considerable overhaul of the multiplayer system with more features and updated networking code to make it more robust under a whole series of circumstances. I can't go into too much detail but it's pretty cool stuff. v1.1 will also include new graphical options including one with very high resolution textures.