He literally said so in an interview with Edge Online, which you can read more about on Kotaku. 
 
I gotta say, I actually kind of agree with him. The jist of what he's saying is basically that he wants to let people begin playing the game up until a certain point, and then give the player the choice to pay so they can unlock the rest of the game. Kind of like XBLA games are already doing,  I think.