I expect to see Space Marines, Chaos, Eldar, Orks. Those are basically the Big 4 of 40k. They're the most iconic and easily identifiable races in the game (The good guys, the bad guys, the elves and the orcs) They're factions that people who aren't already knowledgeable about the game can easily understand. Tyranids are too Alienesque; Dark Eldar are relatively obscure and don't make for good movie level conflict; Necrons are yet another rip-offy race with a lot of roots in Terminator and the Tau aren't really evil at all, so they're obviously not going to be the main bad guy in any movie.