While carbon fiber is both stronger and lighter than steel and aluminum, it takes significantly more time and money to produce, essentially relegating the material to small-volume cars. The main benefit for trucks is the resulting reduction in weight to improve fuel economy without sacrificing the tough, rugged capabilities truck buyers expect. The Ford F-150 made the switch to aluminum for the 2015 model year and it's proved highly successful. It seemed like it was only a matter of time before the competition followed suit.
Automotive News says that the next-gen trucks will launch with aluminum beds and that it will take a couple of years before we'll see any carbon fiber incorporated into the design. Even then, only look for the composite material on higher-trim models, with a trickle down to lower-spec trucks possible further in the future.
In 2011, GM announced it was working with Japan-based Teijin Limited on a carbon fiber reinforced thermoplastic. There's a good chance that material's introduction will be on trucks.