Currently, Boeing can not replace the 737 with a Carbon Fiber plane because there isn't enough Carbon Fiber produced on earth to keep up with the production line completing three aircraft a day. However, if enough Carbon Fibre could be created to logistically allow Boeing to move away from aluminum I am sure you would see a whole new level of demand for Carbon Fibre. Needless to say, the Carbon Fibre created would need to met Boeing spec, as Carbon Fibre does not have a single global quality standard, unlike aluminum (thank you WWII).