I think all those Steve Spielbergs hiding among the 8 billion - without connections and without hollywood names, having their day without getting filtered out by investor gremiums playing it safe - will produce enough material to be happy cineast for life.
Many Internet technologies like Youtube or soundcloud gave content creators direct access to an audience. If you were funny/creative/talented/attractive/in the right place at the right time/etc you could cut out the middlemen and capitalize on that directly. What is the hidden talent these Spielbergs possess that AI will enable? It's doing the writing, videography, etc. I imagine at most these hidden Spielbergs will be filtering output, like looking at a book of wallpapers and choosing what they like. Maybe some great movies get made, but it will just be the result of selection effects on the sheer number being made.
