The expansion will feature new AI Types, new Bonus Ship Types (for selection in the galaxy, etc), and it will also have some overall new things to find in the galaxy itself (Golems will be one cool new thing you can find out in the galaxy and then commandeer for your own use).
There will also probably be some other additions such as Comets and Comet Catchers, and Moons and a few other things that will have some impact on gameplay as well as visuals. Also, I have some ideas about the players being able to get out to the AI's production facilities outside the galaxy, the ability to go through black holes and into asteroid fields, and a variety of other large-scale game mechanics (player-made wormholes, warpships for players, and various other ideas that will significantly expand the gameplay opportunities).
At the moment there is a lot of content coming out, that's for sure, but the idea is that basically the mechanics will be consistent between all of the expansions and the base games, plus all of the ongoing DLC. And before too long, after player requests die down a bit, the DLC will be biweekly and will just have a ship or two in there, plus whatever little mechanics updates/requests players have. The game will continue to grow over the long haul, don't get me wrong, but the pace of changes won't continue quite as it is now for too much longer (unless there's a huge new wave of requests). I'll also have to be working on the expansion, and other future titles, which are all kind of on hold right now just due to the volume of requests and changes here.
Anyway, we'll still be updating more than the big-name RTS games out there (where else do you get free ships on a biweekly or monthly basis?), but presumably this rate of requests can't keep up forever. And, in fact, my list is finally really shrinking down this week, thanks to most of the existing requestors seeming fairly sated by what's already out. I'm sure there will be odd changes pretty much for years, but presumably five or six little changes per week, not 10-15 per day.
We'll see how it goes, I'm basically playing it by ear and responding based on what players ask at the moment. I want to make sure that the existing game is as good as it possibly can be, but the true huge game-expanding stuff will be reserved for the expansions. Hopefully that gives you an idea of my plans with this, anyway.