This article
http://www.apple.com/mobileme/transition.html
includes the following:
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What happens to the pictures that I’ve posted to my MobileMe Gallery?
You can continue using MobileMe Gallery through June 30, 2012, even after moving to iCloud. You should save copies of all photos published to your Gallery before that date. If you have a Mac, it is likely that most of your Gallery photos are already in iPhoto. If not, you can sync the Gallery photos to your iPhoto library. You can also download your photos and movies from the web. Please read this article for details.
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What happens to the files on my MobileMe iDisk?
You can continue using MobileMe iDisk through June 30, 2012, even after moving to iCloud. You should save copies of all files stored on iDisk before that date. Please read this article for details.
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