2) The Knights Of Ren Attack
In The Force Awakens, some handy flashbacks briefly appear when Rey touches Luke’s old lightsaber and receives some Force visions. One of these was Kylo and his Knights of Ren and another saw Luke, shrouded in a cloak, and R2-D2 standing before a fire. We know that these were flashes of the day that Ben Solo turned against his Jedi master and murdered his fellow students as he completed his turn to the Dark Side.
The trailer reveals that these scenes will be elaborated upon in The Last Jedi. After an awesome shot of Kylo threatening an unseen enemy (probably Rey) with his lightsaber, we cut to a clip of a burning building with a cloaked figure and R2-D2 in the foreground. This scene matches up perfectly with TFA flashbacks, so we can guess that that’s the Jedi temple being destroyed and the figure falling to their knees in shock is Luke.
The next scene confuses things, as it’s also set in a burning setting. At first glance, then, it looks to be Kylo Ren and his Knights storming through the remains of the temple. On reflection, though, it’s probably another scene entirely, as it features Captain Phasma leading her troop.