Preview at WWDC likely in June, followed by September launch.
Apple Notifies Former MobileMe Customers of Impending iCloud Storage Downgrade
Your iCloud storage will be reduced to 5 GB on 09/30/2012.With the launch of the iPhone 5 this past weekend, upgraders who have elected to back up their devices to iCloud may find themselves suddenly over the 5 GB limit for free iCloud accounts if their previous iPhone is also being backed up to iCloud. Camera Roll in particular can be a significant contributor to storage needs for iCloud.
However, you are currently using more than 5 GB.
Unless you take action before your downgrade takes effect, backups to iCloud will stop, and apps will no longer be able to save documents to iCloud. You can either free up storage or cancel your downgrade to keep your current storage plan for another year.
Additional information for those seeking to keep their iCloud storage needs below 5 GB can be found in an Apple support document, while those interested in purchasing additional storage space can do so through their iOS device iCloud settings, System Preferences on a Mac, or iCloud Control Panel on a PC. Annual pricing is currently set at $20 for 10 GB, $40 for 20 GB, and $100 for 50 GB. All of the purchased amounts are added to the base 5 GB storage capacity.