When you consider swapping materials you have to do it on a more comprehensive basis than just a single characteristic. Every material we use has a list of physical characteristics and there are ususally for or five that are important to a particular application.
Besides weight there is tensile strength, compressive strength, modulus of elasticity (flexability),and a lot more. Plus you have to consider ability to be glued, screwed, sawed, sanded, lashed etc. Well chosen species of wood give you the most bang for your buck. There is nothing on the horizon that may surpass it at the moment.

: Yeah weight would be an issue. The composite material is 50%-70% heavier.
: However depending on the strength of the stuff you may be able to cut down
: on the size of the wood used and this could keep it within reasonable
: weight. I haven't done the research so I don't really know.