This is only my true concern, that this next installment will be a Warhammer 40k skinned Starcraft clone. I have to admit that this was my impression of the first game years ago, and I wan't entirely into it. I grew to love the series with the second game, I felt it striped the game of unnecessary mechanics to improve others, like the combat, but granted at a cost of the scale of the game.
Now, I don't mind the fact there is base building, I would have been surprised if they didn't put it in at all to some degree. The point I want to make about this mechanic is that I don't want it to be the focus of the game. Like Starcraft, where much of the time you are at base building workers to gather resources, to build a force to attack or expand and build more works to build an even bigger force to attack. This game play loop works well for Starcraft and I feel it doesn't fit in Dawn of War. In Dawn of War, you are out on the field at all times, commanding the front lines and insuring that you have the parts of the map necessary to win. Now, this brings me to my next concern, the new cover system.
They have confirmed cover is returning, which I find great but they have said they are "simplifying it" and making it more "accessible and easier to read" or something along those lines. My main fear with this is that maps will look and feel plain and boring, and matches will devolve into blob fests, where both sides just A-click across the map with their whole army. I will admit that, how much fun I had with Dawn of War's cover system, it did need much more fine tuning. I just wish that this mechanic isn't something over looked with the larger scale, and still remains important. Improving it to allow good path finding, balanced, and still be important across the map.
That's pretty much it. I'm still excited but cautious.