That's kind of a loaded question. A child that has autism is no more guaranteed of having a superior intellect than is a child that does not have the disease. Children that have autism can vary in the affliction and manifestation of the disease by degrees, from severe to mild. I am sure the intelligence level, as it does with children who are not afflicted with autism, probably varies as well, with some performing at what could be described as a superior level, some at a minimal level, but a lot performing somewhere in the middle of the performance scale.
We should also recognize science is a perpetual, self-correcting discipline. Just about the time we think we have all the answers to the questions, they go and change all the answers! The effort to try to understand a problem such as autism should be the main focus, and as we uncover things that make better sense about it, we should go back and correct our previous understandings. So will science ever really know? At this point, it is a rhetorical question, in the same category with finding a cure for the common cold.