Based on the 60 seconds of footage in the trailer, this is what I think will happen in the movie.
Movie starts with the Enterprise in grave danger, lot of internal explosions... the ship is going down.
The Enterprise crashes into the water, nosediving at one point.
Rooms and corridors are turned 90 degrees when this happens, causing people to fall.
Kirk is holding on for his life while trying to grab other people, preventing them from falling.
But he is unable to catch Gary Mitchell who falls to his 'death'.
The Enterprise is flooding and everyone will die unless Kirk (I believe) or Spock (see image blow) sacrifices themselves Wrath of Khan style.
Uhura and Scotty are devastated, whether it's Kirk or Spock, either way that person somehow survives.
The Enterprise survives and rises from the water.
Kirk giving a speach at a memorial for all the lost crewmembers who died during the crash.
Complete with futuristic jets flying overhead.
Having lost a lot of it's crew due to the crash, a lot of replacements are newly assigned to the Enterprise, including Elizabeth Dehner.
Who Kirk immediately takes an interest in.
And the Enterprise returns to it's routine missions, lot of running and jumping.
Gary Mitchell somehow survives the beginning of the movie and attacks Starfleet Command, blaming Starfleet and Kirk for leaving him for dead.
Kirk wants to go after Mitchell, but Admiral Pike orders Kirk not to.
Mitchell heads to a Klingon outpost which he infiltrates then blows up.
Leaving their Starfleet uniforms behind, Kirk, Spock and Uhura disobey Admiral Pike's orders and heads after Mitchell to find out why he's attacking Klingons.
Spock trying to capture Mitchell in the ruins of the Klingon outpost.
Gary Mitchell captures Kirk and Uhura.
Kirk and Uhura look shocked while Mitchell tells them how he's going to get his revenge by tricking the Klingons to declare war on the Federation.
Spock eventually catches up to Mitchell and outwits him. Spock holds Mitchell at gunpoint while Kirk beats him up a little bit for all the stuff he's done. Mitchell is captured?
In order to save the Federation from being blamed for the destruction of the Klingon outpost and prevent a war. Spock goes inside a volcano to trigger an erruption to destroy what remains of the Klingon outpost, erasing any evidence of what Mitchell did to the place.
His revenge foiled, Mitchell escapes back to the Enterprise where he takes Kirks new girlfriend, Elizabeth Dehner hostage.
Kirk walks onto the bridge of the Enterprise to confront Mitchell once and for all.
Only to find Mitchell wearing a Starfleet shirt, sitting in the captains chair on the bridge, waiting for him.
Final battle begins. Kirk Vs. Gary Mitchell.
What do you all think of my theory? :-)

Movie starts with the Enterprise in grave danger, lot of internal explosions... the ship is going down.

The Enterprise crashes into the water, nosediving at one point.

Rooms and corridors are turned 90 degrees when this happens, causing people to fall.

Kirk is holding on for his life while trying to grab other people, preventing them from falling.

But he is unable to catch Gary Mitchell who falls to his 'death'.

The Enterprise is flooding and everyone will die unless Kirk (I believe) or Spock (see image blow) sacrifices themselves Wrath of Khan style.

Uhura and Scotty are devastated, whether it's Kirk or Spock, either way that person somehow survives.

The Enterprise survives and rises from the water.

Kirk giving a speach at a memorial for all the lost crewmembers who died during the crash.

Complete with futuristic jets flying overhead.

Having lost a lot of it's crew due to the crash, a lot of replacements are newly assigned to the Enterprise, including Elizabeth Dehner.

Who Kirk immediately takes an interest in.

And the Enterprise returns to it's routine missions, lot of running and jumping.

Gary Mitchell somehow survives the beginning of the movie and attacks Starfleet Command, blaming Starfleet and Kirk for leaving him for dead.

Kirk wants to go after Mitchell, but Admiral Pike orders Kirk not to.

Mitchell heads to a Klingon outpost which he infiltrates then blows up.

Leaving their Starfleet uniforms behind, Kirk, Spock and Uhura disobey Admiral Pike's orders and heads after Mitchell to find out why he's attacking Klingons.

Spock trying to capture Mitchell in the ruins of the Klingon outpost.

Gary Mitchell captures Kirk and Uhura.

Kirk and Uhura look shocked while Mitchell tells them how he's going to get his revenge by tricking the Klingons to declare war on the Federation.

Spock eventually catches up to Mitchell and outwits him. Spock holds Mitchell at gunpoint while Kirk beats him up a little bit for all the stuff he's done. Mitchell is captured?

In order to save the Federation from being blamed for the destruction of the Klingon outpost and prevent a war. Spock goes inside a volcano to trigger an erruption to destroy what remains of the Klingon outpost, erasing any evidence of what Mitchell did to the place.

His revenge foiled, Mitchell escapes back to the Enterprise where he takes Kirks new girlfriend, Elizabeth Dehner hostage.

Kirk walks onto the bridge of the Enterprise to confront Mitchell once and for all.

Only to find Mitchell wearing a Starfleet shirt, sitting in the captains chair on the bridge, waiting for him.

Final battle begins. Kirk Vs. Gary Mitchell.
What do you all think of my theory? :-)