Looks like Apple is set to reset iCloud backup data on Thursday, September 22nd, as seen on the Apple Developer forums, according to 9to5Mac:
On Thursday, September 22, the iCloud Backup data will be reset. Backing up to iCloud or restoring from an iCloud backup will be unavailable from 9 AM PDT – 5 PM PDT. If you attempt a backup or restore during this time, you will receive an alert that the backup or restore was not successful. After this reset, you will be unable to restore from any backup created prior to September 22. A full backup will happen automatically the next time your device backs up to iCloud.
Previous rumours have stated iOS 5 GM would be released on Friday, September 23rd, so this reset of iCloud data looks to be a preparation for that, as so far we’ve seen 7 betas. Apple has stated iOS 5 will be released in the Fall, and many have speculated a simultaneous next-generation iPhone launch to go with it.
As for the launch of new iPhones, rumours have speculated an October launch with possibly two models to be available, one an iPhone ’4S’ (as seen on AT&T’s internal systems) and a completely upgraded iPhone 5.