RHEL 7 repos are not available after upgrade from RHEL 6

Issue

• RHEL 7 repos are not seen after following article 637583 to upgrade to RHEL 7.x from the latest version of RHEL 6.
• After upgrade to RHEL 7, the repos seen are still those of RHEL 6:

# yum repolist 
Loaded plugins: product-id, subscription-manager
repo id                                repo name                          status
rhel-6-server-eus-rpms/7Server/x86_64  Red Hat Enterprise Linux 6 Server  0
rhel-6-server-rpms/7Server/x86_64      Red Hat Enterprise Linux 6 Server  0
rhel-server-dts-6-rpms/7Server/x86_64  Red Hat Developer Toolset RPMs for 0
rhel-server-dts2-6-rpms/7Server/x86_64 Red Hat Developer Toolset 2 RPMs f 0
repolist: 0

• Trying to enable a repo manually shows:

# subscription-manager repos --enable=rhel-7-server-rpms
Error: rhel-7-server-rpms is not a valid repo ID. Use --list option to see valid repos.