iTunes Leak Points to Automatic App Updating in iOS 5
A MacRumors reader tipped the site to the fact that when asking iTunes to check an end users' app library for updates, the following line had been added to the My App Updates results page (since pulled):
Or if your device has Automatic Download enabled for apps, your updates will download to your device without having to sync.That's not a feature of iOS 4.3, so it is likely one for iOS 5.0.
Android can optionally update apps on an Android device (unless a manual update is required because of a permissions change) so Apple is playing catch-up here. It's unclear if the setting would be app-by-app, as with Android, or overall.

Apple is expected to spotlight iOS 5, as well as iCloud and Mac OS X Lion on Monday during the WWDC 2011 keynote, at 10 a.m. PST.