Well, there's been two DLC released for Rebellion, Forbidden Worlds and Stellar Phenomenon. However, future DLC seems highly unlikely since the game engine is basically stuffed to its capacity. It is possible we'll get some multiplayer related updates from Stardock's project Tachyon, but specifics on that have been vague.

The devs have said there is a hint to what is chasing the Vasari in Rebellion somewhere, but if anyone has found it, the devs have not confirmed it. It is likely one of those things that we won't know for sure until Sins 2.

Fortunately the modding scene for Rebellion is better than ever. One bright side of no more game updates is that modders can work without fear of having to update their mods to the latest patch. What sort of mods would you be interested in. Enhancements (more research, planets etc), new races, total conversions (mods that remove all Sins content and replace them with something else, usually from many sci-fi universes).

Sadly not a lot of mods have added totally new ship types to the existing factions, mainly because its hard to make a TEC/Advent/Vasari ship design from scratch and still have it look like it authentically belongs in the game. However, there are two major mods that other Enhancments like more research, abilities, etc. to the original factions, the Enhanced 4X Mod and Distant Stars. They also add new planets and other global things like that. They're a good start if you want to try mods yet not be faced with totally new stuff, since the Sins races are still there.

** Full disclousure, I'm the author of the Enhanced 4X Mod. **

Sins of a Galactic Empire is indeed a Star Wars total conversion. There's actually 5 Star Wars mods I think with releases on Rebellion, Star Wars: Interregnum and Ascendancy being the other big two you may want to look into for Star Wars. There's also well respected conversions for Star Trek, Halo, Battlestar Galactica and a few other franchises.

Thanks Goa I'll have to look those two up and definitely get my mod feet wet with them, and yea I can imagine it would be quite the task to get a solid faction ship that looks original and authentic, might try out the other conversion ones, but for now I believe I'll use the one you authored and probably that distant stars one as well.