Looks like a pretty straight remake of X-Men: The Last Stand. I'm guessing it's Erik who dies this time, in an Into Darkness-style AU fliparound.
I actually think Mystique is going to die. If you watch the trailer closely some clues and hints are given. There is a funeral where Charles, Hank, Storm, and Cyclops are present. It is raining. Then, Charles and Hank (while in the same outfits and wet) have a conversation at a table and Hank blames Charles. Given his close relationship with Raven (Mystique) in the previous three films it makes sense that he would be angry at Charles for Mystique's death. As the de facto leader of the X-Men, her death would raise the stakes, show how big of a threat Phoenix is, and also make way for Cyclops to eventually become leader of the team.
As for the trailer, I enjoyed how it is more somber and character-driven than I thought it would be. I am assuming they will save the more action-oriented scenes for the next trailer. I also have to echo
DigificWriter's sentiments and relay how sad I am this particular series is coming to an end. I distinctly still remember watching the very first
X-Men in the theater in July 2000. It's crazy to think this series has been ongoing for nearly two decades.
Dark Phoenix will be the twelfth film.
I'm sure there are many comic-book aficionados that are excited for what Disney and Marvel will do with the property. I am as well, but to be frank I'll miss James McAvoy as Xavier and Michael Fassbender as Magneto. These actors really inhabited their roles and their chemistry was the best part of these recent films. Whoever they get to replace these actors, including Nic Holt as Hank McCoy, Evan Peters as Quicksilver, Jennifer Lawrence as Mystique, etc., will have big shoes to fill.