From what infos I so far gathered here are some of the things we should expect to hear about at Apple's "Let's Rock" event at Sep9.
1. iPod Nano Slim will be announced
2. iTunes 8.0 will be announced
3. iPod Touch prices drop due to new iPod model
4. iPhone 2.1 firmware update announced (Possible only for beta testers first)
Well with less that 40 hours left I am guessing that's pretty much all the leaks you'll get UNLESS Steve has a dark little secret for us :P