RHEL 7 was released on June 10[1], but many people (myself included) don't have a RedHat subscription and run CentOS, the 'community' edition of RedHat.
Up until today, CentOS 6.5 was the latest release... so I can start using CentOS 7 now and enjoy the benefits that RedHat introduced in RHEL 7. You can see that the delay before CentOS releases a community version of RHEL has been much improved in recent years in this Wikipedia chart[2].
Also, iirc, this is the first major CentOS release with the CentOS project more or less under RedHat's wing[3].