The swarming genestealers are the basic combat unit but you can see a few different ones in the trailer, the hybrids sit back and behave more like soldiers using normal weapons plus there's the much bigger broodlord and patriarch's. They've never shown or suggested them but I'd be very surprised if there's not Chaos marines you're put up against, the Deathwing are not Xenos specialists (while many other are and Space Hulk has always traditionally featured the Blood Angels) and their primary objective is always to find Traitor Dark Angel marines.
I am concerned that while it may look great the gameplay may be poor and ultimately that's what really matters.
Used correctly terrain is a second weapon in your arsenal, equal to your Titan itself. Make the battlefield work for you, or you will find it working for your opponent.