Here's a clue:
Sept. 5 - Latest date Governor General Michaelle Jean heads to Beijing for Paralympics.
Sept. 11 - Governor General Michaelle Jean back in Ottawa (and ready to dissolve Parliament, if need be.)
Not only are those two dates on either side of the by-elections on the 9th, but if you count forward 36+ days from when Harper seems to want the writ dropped (the 5th), and given that an election will be on a weekday, you end up with October 13th or 14th as the earliest election day.
If he doesn't manage to catch Jean before she leaves for China, then we'd be looking at October 20th. What happens between those two dates?
Oct. 14 - Tentative release date for Julie Couillard's autobiography
There ya go. Not the whole answer, but certainly one of the more entertaining scenarios.