I agree that initially, standard seating on the DC-10 and B777 was 2-5-2. But the DC-10 went away, and seating on the B777 has generally changed to 3-3-3 (or 3-4-3, a configuration that I avoid like the plague).
I still believe that despite a huge increase in emergency exit doors, you will still need double-wide aisles in order to have efficient PAX loading and unloading, as well as avoiding complete aisle blockage by service trolleys.