This actually sounds pretty good to me. Ideally in a laptop you want to get rid of the heat through the vents, not through the case. Nobody likes burning their thighs and/or wrists, and that's a big problem with the metal macbooks.

Now I come to read the article more carefully, in fact, the part they're considering replacing with carbon fiber is the bottom cover, which suggests they really are thinking in terms of heat conduction, even though that's not mentioned in the article.