Yes, I was thinking about the 12th, too, but not as many people will be watching the closing ceremonies as the soccer game, and people's emotions will be very high for the soccer game (aggression is a major channel for demonic activity).

However, the game will be played on the 12th in time zones like Australia, Korea and Japan (the 11th in London and US, etc.), so you might be on to something there. The start of the Mayan long-count is variously given as August 11th or 12th.

In any case, this is all pointing to something not good. Hope it's just my GLP-fueled paranoia kicking in again!