Short answer: Some traits of Asperger's are found in those with high intelligence, and vice versa. In the grander scheme of things, however, it appears that correlation does not imply causation.
Longer answer:
AS was first described in 1944 by Austrian physician Hans Asperger. He considered it to be a personality disorder characterized by pedantic speech content, impairment of two-way interactions, excellent logical abstract thinking, isolated areas of interest, repetitive and stereotyped play, and ignorance of environmental demands. AS individuals were thought to be capable of originality and creativity in selective fields (Tsai, 1992). Asperger (1979) suggested that his syndrome was more likely to be observed in children of high intelligence and special abilities. However, to date, the clinical literature on AS has focused on children with average or low-average intelligence. There has been surprisingly little examination of AS among gifted children (Barber, 1996; Cash, 1999a; 1999b).
There seem to be at least seven characteristics that are common to both gifted children and children with Aspberger's syndrome. Those are: verbal fluency, a fascination for letters or numbers and/or memorizing information, an intensive interest in a specialized topic, hypersensitivity to sensory stimuli, a large range of abilities due to their specialized interest(s), and uneven social or affective development.
Due to this overlap (and not necessarily in spite of it), Asperger's syndrome is often mistaken for giftedness in children.
There are differences between gifted children without AS and non-gifted children with AS. Unlike gifted children, children with AS often demonstrate motor clumsiness, low tolerance for change or agitation, inability to understand social humor and proper affect, and appear to lack a "theory of mind" (in other words, they may act abnormally and not have any clue that others perceive them to be abnormal).
Perhaps the most pronounced feature to distinguish a gifted AS student is his or her remarkable lack of insight and awareness regarding the feelings, needs, and interests of other people. An AS child will talk interminably in a monotonous or pedantic tone about a favorite topic, unaware that the listener might not be interested, needs to leave, is bored, or wants to say something. AS children will also interrupt private conversations and enter or leave abruptly without concern for the wishes or needs of others. They seem oblivious to the simplest rules of social conduct, and repeated efforts to instruct them or remind them do not change these behaviors. A pronounced lack of social awareness is not a common characteristic of ordinary gifted children.
Based on this, it does not seem that AS foreshadows high IQ. It seems likely that AS is often misdiagnosed as giftedness/high intelligence, or vice versa, considering the overlap in external behaviors among both groups. In addition, if 100% of your mental energy was spent on one or two very specific interests, and if you set about in such a way that you /only/ talked about those interests whenever possible, you would indeed seem very intelligent and competent. :)
