I know this topic has been hammered to death, but here's my take on it:
We know Barricade got an ass whupping from Bumblebee, but then was present when the Decepticons rallied and we see him on the freeway just before Prime and Bonecrusher fight.
After that he is not seen again, and there are no pieces visible on the ship when they are disposing of the wrecked decepticons. The only pieces seen are of Blackout and Megatron.
According to the book he was killed by Prime after he had killed Bonecrusher, hence the reason Prime was late into the city.
But the book isn't the film, and doen't have to be the same, the producers can easily bring him back for the sequel... along with Scorponok and Starscream.
I hope the do too as I thought Barricade was too cool for school