Ok I'm playing this now.
You can definitely see the holes where they are going to put the DLC...
I could honestly go either way with Paradox's DLC approach, but that's neither here nor there. The modability is nice. I'm looking forward to the Star Wars, Star Trek, Babalon 5, Dr. Who, and Battlestar Galactica mods. And certainly the mod that ties them all together.
It seems to me that the time scale is really small. I put a game on fast-forward last night and it reached the tech ceiling in only a couple hundred years. I suspect that the top of the tech tree is going to be a "star gods" expansion. That's pretty trivial, though; the only inexcusable flaw with the game as it stands is probably the lack of a "planets" screen to show all colonized words at a glance.
Speaking of colonies, it bugs me that you can't colonize Mars, but you can build "frontier outposts" on stars, but those outposts require tons of influence, but building colonies requires none. Get into two alliances and play an edict, and boom, no more expansion in the early game unless you happen to find an absolutely perfect planet right next door.
Going back to the tech tree, this game is crying out for CK2-style regional tech levels! It'd be awesome to forbid the colonies from getting hyperdrive technology so they can't rebel, and it would stretch out the tech game if empires could rise and fall on the technology tree.