A vehicle supplement would be nice, especially one with rules for aircraft. That said, this looks fun too. I'm sure they've got room on the schedule for both.
So far, three of five pre-written adventures have been against the Dominate. Out of all of the 'paid' books (GM Kit, Final Testament, No Surrender) they've exclusively been about the Dominate. I expected a bit more diversity honestly.
Let's be fair, the GM Kit has the squad eventually going up against Eldar (or, y'know, fleeing in terror from them) and Final Testament is just as much a fight with the orks as it is with the Dominate. More so in many parts, since the Dominate's trying to be subtle. Hardly exclusive...if anything, the orks are the ones with the most screen time. Which makes sense - they are, after all, the orks.
I wouldn't be surprised if we get a B-plot or twist that pits the squad against something other than the Dominate near the end. The shadow over the Guardsman on the cover certainly looks like a Chaos Space Marine, but there's plenty of room for surprises. What if one of the Dominate's leaders on the starfort was one of the Fallen, for instance? The squad gets unexpected support from the Dark Angels throughout the first two acts, ends up being sent in to assist in securing an enemy commander, and suddenly one of their comrades or an NPC takes a bolter round to the back of the head...