Its combination of durability, strength, and lightweight are appealing to firearms manufacturers and shooters alike. However (and speaking as a manufacturer myself), it is a royal pain in the ass to manufacture and machine (it causes small fibers to particularize which can ruin most standard CNC machines without appropriate filters, vacuums, etc.)

NASA is stepping up to the plate with new looms capable of creating complex shapes out of carbon fiber. Complex shapes normally are very difficult to manufacture due to the way carbon fiber is layered onto a base mold. The shapes make it difficult for hand-weaving as humans cannot hold enough tension on the fiber without causing folds/wrinkles in the layers.

While it will take a few years, this kind of technology will filter down into making carbon fiber stocks, handguards, and other complex shapes such as grips. In fact, I would postulate carbon fiber will be common to see on firearms in another decade or so without a premium price tag.