updated 02:56 pm EDT, Wed September 11, 2013
Apple lists feature as 'coming soon' on iOS 7 website
iCloud Keychain support has been removed from the iOS 7 gold master, users note. The option has gone missing from iOS 7's iCloud preferences. Apple has also marked Keychain as "coming soon" on its iOS 7 website, implying that the feature won't be in the public release of the firmware or in any near-term point release.
The technology expands on the original OS X incarnation of Keychain, letting people carry usernames, passwords, Wi-Fi logins, and credit card numbers across devices. Apple has presumably encountered trouble implementing it though, and decided to avoid postponing the iOS 7 launch. The next release opportunity may be alongside the introduction of OS X Mavericks, which should arrive in October or November and carry the same feature.