Both are grammatically correct, but they mean slightly different things.
However, it is forecast that in the nearby future an advanced artificial intelligence will arise: AI that transcends human beings.
This means that the technology will exist to surpass human intelligence. It's like saying that stone age axemaking was surpassed by bronze age axemaking. Artifical Intelligence, the art, will transcend human beings.
However, it is forecasted that in the nearby future advanced artificial intelligences will arise: AIs that transcend human beings.
This means that some individual artificial intelligences will surpass humans. It's like saying that stone age axes were surpassed by bronze age axes. Artificial Intelligences, the algorithms with their data, will transcend human beings.
It seems like you can't have one be true without the other being true, unless we have a few outliers and we don't know how to consistently construct them.