If you are using the iOS 8 beta or OS X Yosemite preview intended for developers, then you should already be aware that Apple released an email explaining they’re about to perform an iCloud data wipe. The deletion of server-side data will take place on July 7 and will remove all information contained on private databases along with CloudKit public databases.
This means any data you have held on Mail Drop, iCloud Photo Library and iCloud Drive will be removed in 2 days time. With this in-mind, it’s a good idea to make sure everything is in order with your devices and maybe even make another local backup through iTunes.
Those of you with videos and photos held in an iCloud Photo Library will be glad knowing the content will remain on the local storage of iOS 8 devices, although this is a no-brainer really, but we’d still recommend you make sure you have a recent local backup.
Once the data wipe takes place, Apple state your content will upload to the online Photo Library “automatically”. You might need to re-activate iCloud Drive from Set Up Assistant after July 7. Data and documents will automatically upload to iCloud Drive if you choose to store them there.
Another point to note: earlier OS and seeds won’t see iCloud Drive update, so you’ll need to resend attachments after the upgrade thanks to Mail Drop expiring.
Also See: iOS 9 beta 6 likely for testing partners