Now set in the near future, based on the trailer and only watching it once as of right now, the single player story seems to be about some enemy taking control over the unmanned drones of the US military, and I would assume that you're fighting to take back control.
Its an interesting choice, and I know it leaves a few people hesitant on the actual game. But here's the way I look at it. The Call of Duty series has always been about hyper reality. The tech they portray in the game is realistic, and its just the characters and events that are the fiction, so will we see really futuristic weapons like lasers and such? No. We'll see a lot more drones, since that is something the US military is actually expanding to now, but at the same time, you'll still be shooting bullets and rockets in the game (with the exception of zombies).
Also, given that this is just the single player preview, and I don't spend more than six to eight hours in the single player versus the hundreds/thousands of hours in multiplayer and zombie modes, this trailer doesn't change my mind about buying the game. I'm just hoping Treyarch learns from what was wrong with MW3, and moves things forward.