It really depends if Apple announces that they are in stores on the day after the keynote or at a later date. If its like last year, Apple stores will get them the day after the keynote, and most Best Buys 2 days after the keynote. (Guessing some get them the same day as apple stores). At least thats the way it was where I live.
If they release them a few weeks after the keynote, I would guess they would be at Best Buys and apple stores on launch day.