I am almost sure that they won't take away eMail addresses from people already registered... The would be brutal, forcing people to move to another mail service. They may charge for some extra features in mac.com mail or for more mail storage space. I hope I don't lose my mac.com website either.
Oh my gosh! I just went back to my site and the "made with .mac" is gone replaced by "made with apple iTools!!! It must have been accidently done too early!