Well we had insiders on gaf months before e3 saying this would happen. Now we have proof that at least some games were on high end pc.
Seems a little fishy to say the least.
We also have proof that one of the best *looking* games at the show was running on XBO hardware so i'm not sure exactly whats been proven except that not everyone has final hardware yet. Will games look better/worse than they did at E3? Maybe but thats true of both platforms and was true 7 years into the current generation too.