The mystery continues. Here's what I get when I go to "iCloud > Manage > Change storage plan:"

When I saw that, I thought "Fine, they'll automatically renew and charge me on Sept. 30th."
However, when I go to "View account," I see this:

I suppose iCloud will automatically renew and charge me, but it's certainly not clear from their email, from their "For more information" article or when I view my account in System Preferences.
My view in the blue "20 GB" screen shot might be different from the one in the Tech note because I signed up for the 20 GB plan last year. I think it was before they announced the free 20 GB for MobileMe users. I clicked to purchase the plan but was not charged the $40. Obviously, though, I was entered into the 20 GB automatically renewing plan.
But why then did they just send me the email saying:
| As a thank you for being a former MobileMe member, you received a 20 GB complimentary storage upgrade when you moved to iCloud. Your upgrade expires on September 30, 2013. |
| When it expires, your iCloud storage will be automatically adjusted to the free 5 GB plan. Note that you are currently using 17.38 GB of storage. If you exceed your storage plan on September 30, 2013, iCloud Backup, Documents in the Cloud, and iCloud Mail will temporarily stop working. |
| To continue using these iCloud features without interruption, reduce the amount of iCloud storage you are using or purchase a storage plan by September 30, 2013. |
Only Apple knows....
Thanks to you and Kappy for your responses.
Don