I doubt anything will top Beijing for long while, simply because they put everything into their Olympics. The size, complexity, and coordination are really second to none. That said, it's exactly why London chose to make their ceremony the way they did. They knew it, and they didn't try to compete with it in the same ways. I was impressed with the ring forging from London, but the show wasn't as "big" as either Beijing or Sochi. Sochi is definitely bigger "feeling" to me than Beijing, but only in the scale, they went for a very large feel with minimalist elements (the elements themselves not always being minimal by any means).
Pity it will probably be remembered for its failures rather than the technological marvel that it is.