Students will continue to receive the standard computing services for as long as their department has them listed as "Active in Program." This means that students who don't take classes during the summer continue to receive the standard computing services during the summer.
Students who leave the University will stop receiving some standard computing services when their department stops listing them as "Active in Program." Alumni are able to maintain access to some of those services. See What Happens to Your Uniqname, Directory Profile, and Computing Services After You Leave U-M.
Emeritus faculty continue to receive the standard computing services.
Retired staff receive a smaller set of computing services that includes Google Apps UMICH.
Faculty and staff who leave the university permanently will continue to receive the standard computing services for approximately one month. Prior to the end of this month, you'll want to make sure you close out your account so as to forward new email, archive your old email, websites, etc.
If you still have questions as to how your situation will affect your access to computing services and what options are available to you, contact the ITS Service Center for more information.