Plus,
1) There were several others on here that said it was going over 700m. They just didn't use the word lock. But they were pretty adamant it was going over.
2) In one of his posts, he was even using an Oscar re-release to justify why it was getting there. He wasn't calling for it on Labor Day. Hell, Avatar will hit 800m if they keep do re-releases.
3) We all have our hits, and we all have our misses on our "locks". It's the box office.