You can count on Apple using its standard iOS release protocol with its iOS 9 update. Here's what we mean by that.
You should expect Apple to release iOS 9 for every supported device at the same time. If this is your first major iOS update, note that Apple does things a little differently than Google and its Android platform. Everyone will get iOS 9 at the same time.
You can also count on an iOS 9 release time that falls somewhere between 9AM PST and 10AM PST. Apple probably won't confirm this on stage during the event but this is when you can expect the iOS 9 release time to land.
You can also expect the iOS 9 update to emerge in your device's settings and through iTunes. With iOS 9, Apple's cut down the amount of size required to install Over-the-Air so things should definitely go a lot smoother for those of you that don't have a lot of free space.