Somebody correct me if I'm wrong, but my reading of the article was this:
Yes, the conductivity decreases as temperature increases with this material... as it does in pretty much all conductive substances, copper included. Now, if you'll pay attention to the last paragraph: at 77C, the copper/graphene material had a conductivity of 440W/mK. Now, at *27C* (much cooler), pure copper has a conductivity of 380W/mK. So even at a much higher temp of 77C, the copper/graphene had better conductivity than copper did at a much cooler temperature.