I seriously hope when he says large he means LARGE. After the amount of time I spent in the uncanny valey *caugh* I mean Cyrodiil of Oblivion and Fallout 3 I came to hate the subtle weirdnesses of that engine. I was hoping for a completely new engine, or id tech 5. But if he says large lets hope he means that the engine will be almost unrecognisable.
When he said large (actually I think it may have been major), but he emphasized MAJOR. "MAJOR changes to our basic technology".
Todd also said, "We're very aware of our technical deficiencies".
And of course, spoke directly of revamping the animation system as an example when he said they're aware that the NPCs in their games don't exactly behave that well on screen, so they want to fix that.