Facebook has announced that they are rolling out an update which would mean that users would get the same address for their profile and Facebook email address.
For example if your username on Facebook is xyz123, your Facebook email address would be firstname.lastname@example.org.
This update would not affect users who have already selected their email address manually.
Facebook rolled out their email product a while ago though it has not really caught on. Facebook too has remained relatively quiet about it with no major features added to it since launch.