You also see a sniper killing people with one shot, a guy back flipping over a rocket, and a rocket launcher for that matter. None of these things are going to be a part of the game. The trailer was commissioned and created while the game was still in a design phase, and before they got into balancing. You're not beyond your rights to ask for confirmation, but the best i can tell you is that it has been confirmed in the past, and don't really feel like searching through countless interviews to find the quote.
Not gonna make you search, lol. If you say its been confirmed, I'll roll with it. svcks its not in there, but I guess I'll make do with a machine pistol. Everyone says they're going light body type more than anything, but I get the distinct feeling that a lot of people will fall back into a more normal play style, using SMART just to move across the battlefield slightly quicker (which, I know, was a huge incentive for its creation).
I myself was/am looking forward to either:
A ~ Duel wielding pistols and using SMART to navigate quickly around enemies confusing/lighting them up. Still be doing this, just with machine pistol as I said.
B ~ Using SMART to find high up little hidey holes above the battlefield and soften up the frontlines with a turret+short rifle combo.