What will happen to MobileMe mailboxes in MacMail when MobileMe goes away this year?

Question

I use the Mac mail application to handle and store years of messages for business and home use. Currently, I store the bulk of my e-mail archives, which I use regularly, on my Mac, rather than on MobileMe (which is what appears in the Mail application in the Mailbox List).
I love the ease of Time Machine, but recently had a serious outage after a series of power surges, which destroyed thousands of dollars of electronics in my home. My computer equipment had surge protection and came through fine, but I still worry about the fragility of storing data long-term in the same location as my work and home computers. I'm increasingly looking for cloud-based solutions for secure long-term storage and back-up. I've experimented with Drop Box and have migrated to iCloud, which works so much better than MobileMe that it's stunning.
Specifically, regarding the Apple Mail app, I split my storage of e-mail archives between mailboxes "On My Mac" and in "MobileMe." Can I move the Mac-based archives to "MobileMe," or will those mailboxes go away with the final transition to iCloud and the disappearance of MobileMe? And if those are to continue as a feature iCloud, can I be sure those archives (including file attachments) will be available to me in the future without worry about corruption or other data loss? 
Thanks.

Answer 1

My issue is not moving folders from .mac to iCloud. The issue is that in the Mail app, my Folder List shows messages can be stored either "On My Mac," i.e. stored locally on my hard drive, or on "MobileMe," which is in the cloud. However, since I have migrated to iCloud, why does the Mail app continue to show my cloud-based e-mail storage under "MobileMe."
This raises the obvious question as to whether these archived folders labeled "MobileMe" will disappear when MobileMe fully shuts down this year. Does anyone have documentation addressing this question. If the folders listed under "MobileMe" are indeed in iCloud, why aren't they now labeled "iCloud," instead of "MobileMe"?
I don't believe this is an obvious question. For example, my understanding is that any files I have currently stored in my iDisk space on MobileMe will be lost at the shut-down of MobileMe because the iDisk app will not be supported in iCloud. At present, those files and my iDisk folders are accessible to me, even though I've migrated to iCloud and can no longer sign into other legacy MobileMe services, such as http://me.com/mail.
To be clear, I'm not looking for opinions or guesses about what might happen when MobileMe shuts down. I'm looking for Apple documentation on what services and legacy data stored in the cloud through MobileMe will be available in iCloud post-shut-down and what steps need to be taken in advance to ensure that I don't lose data.
Thanks.