When they talk about the movie being "bolder" I too tend to think about one of the main cast dying -- and the dress uniforms really do seem like something they'd wear for a funeral --
In the set pictures we saw Spock, Kirk, Chekov and Scotty wearing that uniform though, so we could exclude these characters.
Theoretically, anyone could die here including Spock but:
Spock already died in the prime universe. If the writers really want to make something different and their own star trek, re-making the same storyline would be a big risk.
Also, after all the talk about the Kirk/Spock's friendship, killing one of them
now would be stupid. They aren't even friends, yet.
They could kill off Uhura and give Spock manpain but:
- she's the only main female character and she's a woman of color, THIS woman of color in particular with everything her character had represented in the original series and the time when it was made. They could kill her yes, but it could be perceived as gross and sexist to kill
her especially after all the talk about her getting more space than TOS Uhura.
- Enough with Spock drama. His mother died in the first movie and his home planet got destroyed. You kill his girlfriend
too, now? What's next? His suicide? And It's not like his character isn't already complex, you don't need to kill his whole family and friends to give him "manpain".

The poor man is drama with legs.
There are other characters there, and perhaps it's time to give some dramatic plot to the others too (if it is
really necessary).