As an old fan of DoW franchise i would like to have a few words on how i belive the game might be improved based on what i have seen on the gameplay trailers.
First off, when you are making a game in a universe so rich in lore like 40k, it is best to stay true to it. To help that i would recommend on cutting and tweaking some of the space marine running animations as well as considering changing Gabriel's somewhat comical slam jump into a teleport or charge.
Second, give us the option to turn off outlines on marked units.
Third, consider equalizing the "important character's" and the infantry height a little bit. While i understand that this height makes them stand out, i belive that it has gone beyond what is acceptable and needs to be towned down.
Thats my 3 cents on the game so far and im excited, but cautiously worried.
So the most recent trailer lends a few possible clues as to what Necrons will look like in DoW 3.
This is all pure speculation but a few details seemed interesting in the video:
Ok, knowing a bit of Necron lore I can draw the following remarks. Firstly the orange lights of the terrain lead to the Mephrit dynasty, thone of two  current known dynasty of Necrons to use orange  as opposed to green energy cores. This is because they harness solar energy and use it for their means. The Mephrit dynasty is also best known for being and I quote : "pitiless planet killers"  , destroying countless planets. So far seems to fit, The orange lightning in the rift is a bonus. Also in the end shot with all the floating rings, beams of orange energy are coming down which look different to the ability of the Space Marines. It's almost as if they are feeding a dormant tomb world, which is coming back to life, it's lights are turning on and floating rings be floating. My guess is then the Mephrit try to destroy the planet or something else and the three factions have to try to stop them. Speculation and it's not much but seemed too much not to say anything.
 - Imperial Armour 12 - The Fall of Orpheus book, the second dynasty being the Maynarkh however they don't fit planet destroying although they did kill a C'tan. Also they all went crazy with the flayer virus
 - The Necron Codex, 2015 edition