I don't expect it to chance radically. The original SotS lacked depth. There was literally nothing else to do but build ships and fight. While the total war series is also all about conquering the known world with force of arms, there still was other stuff to do. Trade, espionage and diplomacy. SotS had none of those and thus felt like a fleet battle simulator. I got boring quickly. I'm hoping the expansion makes the player think a bit more than the next place to attack. Sure, the goal will still be to glass the enemy planets, but if you had the means to effect their economy by raiding, and the capacity to interact with them even a bit, the game would be more interesting.
Actually the trade/piracy system is exactly that.
Planets in secure sectors (no "space monsters" or enemy fleets of large sizes) can build freighters which move between planets and produce income. (which of course is used to build big-blowy-up ships) You can assign vessels to piracy which then impact the economy. (not as much as glassing a planet though)
The added diplomacy is interesting, but mostly focused around a "help defend this" "rally here" "give me money" sort of thing. But there's good "flavor text" for it depending on the race.
There is some information warfare added, since the intel lists enemy technologies you've encountered and also mentions what techs of yours the enemy knows about. So you can play games with denying the enemy info on certain techs you're using by building fleets in remote planets. (and the whole deal of cloaked scouts, stealth ship detectors, etc.) There's not espionage in the "let's do random sabotauge" like in MOO though.
However, the focus of the game is definately on combat. Mostly because the devs wanted to have something like Babylon 5 space-battle wise.