I like the idea of AI but it doesnt fit the current symptoms, it doesnt explain why adult sites are returned for basic searches amoungst other things.
I would also suggest that implementing a big change like an AI algo would be done at a different time to a major infrastructure change - see matt cutts blog a while back where he explains the difference between the different updates, caffine was an infrastructure change not an algo change.
Google is fundermentaly broken, even adwords is broken it isnt returning anywhere near the number of adverts it would normally do and these are obviously non algo influenced.
Re AI i dont think google would have sufficient data on sites to implement it reliably, yes they can measure bounce rate, clickthrough etc but how do you factor in new sites with no data and time on site cant be measured. I can see more ways that an AI type interface can be influenced for long tail than that current system.