Update #1 (8/12/14): It looks like Google deleted the tweet embedded below. Between that and the lack of an update to this support page, someone might have pulled the trigger early. But if those countries don't have access yet, they probably will sometime soon.
Update #2 (8/19/14): After a false start last week, the Play Music expansion now seems to be live. The official Google Play country availability page has been updated to reflect this as well.