The migration to iCloud.com addresses is the second such change Apple product users have seen in the past four years, the first being a 2008 switch from ".Mac" to the soon-to-be defunct ".me" MobileMe service suite.
Apple stopped all MobileMe services on June 30 as the company moved to the more integrated iCloud service which allows for easy syncing between multiple devices. While the transition has not yet been made public, developers were made aware of the upcoming change in Apple's iOS 6 beta 3 that was seeded on Monday. Also revealed in today's change log was expanded settings tweaks for Apple's upcoming Maps app which will make its debut when iOS 6 launches later this fall.
From the update log:
icloud.com email addresses are now available for iCloud mail users. Users signing up for new Apple IDs, or enabling Mail on their iCloud account for the first time, will automatically receive an @icloud.com email address instead of a me.com email address. iCloud users with @me.com addresses that have been used with iOS 6 beta 3 will receive an @icloud.com email address that matches their @me.com address.
Apple's upcoming iOS will feature a revamped Mail app and new iCloud.com email accounts. | Source: Apple
It is unclear if Apple will keep existing .me accounts active after the iCloud.com rollout, but the company still continues such support for legacy .Mac users.