If you've got an iPhone 4 or newer, iPad 2 or newer, iPad mini or a 5th generation iPod touch, today is your lucky day. Apple just released iOS 7 to the wild, and you can grab it right now by either connecting your device(s) to iTunes or going in to your device settings, hitting the "General" tab, and then tapping "Software Update." Keep in mind, the update just went live, and Apple's servers seem pretty slammed right now.
If you've got an older device, don't fret. Apple recently tweaked the App Store so you're not totally out in the cold. Additionally, if you've got a device that's on the lower-end of the spec pool, it might not be a bad idea to hang on to iOS 6 for a bit to see how much iOS 7 impacts game performance.