What determines the progress a child with autism will make from diagnosis?

[asdx2]

Really curious about this ds14 has moderate autism at his diagnosis they also added extreme challenging behaviour, learning difficulties but would argue that he no longer has challenging behaviour and no learning difficulties apart from autism seeing as he's about average for his age group and gifted at maths. It was also felt that he wouldn't ever have "normal" speech but he has now although was around seven before it came.
Dd6 was diagnosed as moderate to severe autism and believed to be less able than ds(same diagnostic team) however on the whole she is far more able than ds even now. So was it purely down to the early intervention or are there other factors such as experienced parents, autism frindly family, personality???
Your thoughts please

(1) The underlying nature of the condition - IQ/however else integrated cognitive ability assessed.

(2) The level/quality of educational/behavioural therapy given.

(3) Factor in that professionals do not have a crystal ball. They do not know how any child will get on.

Just my opinion though, no evidence to back it up.

I don't know if I can link to this, but if you have an ipod there is a downloadable talk by Deborah Fein on the latest research on which children recover.

Ime depends on a) whether the child has imitation skills ( affects ability to learn language) and the severity of other difficulties such as disinhibition, sensory processing, and motor difficulties.