According to a series of code strings found in the latest iTunes beta by The Tech Erra (via 9to5mac), Apple may soon introduce support for app rentals -- allowing users to rent an app for a limited time, test it and, eventually, buy it at full price. A string in particular seems to suggest app rentals may soon be available:
Apps are automatically removed from your iTunes library at the end of the rental period.
The mention of an "iTunes library" also seems to suggest that this functionality may be related to iOS apps, which are stored in iTunes on desktop computers. The lack of trials/demos for iPhone and iPad apps has always been a popular argument against Apple's App Store ecosystem, especially considering recent competitors like Microsoft have introduced support for trials in the Windows Phone 7 marketplace. Rentals would obviously be different from free trials, but they'd allow users to better consider a purchase before clicking the Buy button; it's not clear if "app rentals" would simply be time-based, or also allow developers to exclude certain functionalities from the rental version. The use of "Do you want to start playing the app..." in the code reference is interesting, too.
Apple's iCloud will allow users to instantly push new app purchases across devices, but the company has been unwilling to tackle the App Store demo/rental idea so far. If these strings are of any indication, there's the possibility Apple will announce new app rental features at its media event tomorrow.