This is a bit old (May of this year), but I don't remember seeing anything about it.
The folks at Introversion, makers of the most delightfully stylish and interesting little games, have got another one lined up. A big one. No real clue what it's about.
But there are some tantalizing clues.
Go read this topic. Watch the video. See a city take shape before your eyes utilizing very simple rules that generate a chaotic result.
In about two minutes half of the game Crackdown has been created, with buildings you can actually enter.
Well, okay, not quite half.
Sandbox games utilize simple rules to create complex chains of interesting gameplay. The real bottleneck is creation of assets. If you begin finding ways to create rules that govern the content then you're a step toward simulating the complexity that human designers generate.
I don't think designers will ever be replaceable (I hope not), but I am always looking forward to better tools that allow tremendous flexibility with simple inputs.
Right now game creation tools are crude, the equivalent of hand-cranked film cameras. Everything has to be cut together piece by piece, lit only by candlelight; the medium on which we present things tenuous and prone to error.