This is not correct. The @icloud.com variant is an addition to existing addresses and aliases, and all existing @mac.com and @me.com addresses will be maintained. (There are some instances of existing aliases disappearing and Apple is apparently aware and dealing with this.) No new @me.com addresses or aliases can be created.
As I said, there are some people who have found the @me.com version disappearing - unfortunately you are apparently one of them - but for most people it works OK (including myself). If you care to search the forums you will find several posters reporting that they have spoken to Apple about this and been told that the issue is being looked at (though no firm resoultion time has been offered): for example