Just to update all folks here, CDN is now available on all Managed WordPress plans. We turn it on automatically for new sites. Existing sites can turn it on in their hosting setting (myh.godaddy.com).
Turning on CDN will also turn on HTTP/2 support for all assets except the document. HTTP/2 support is currently in the works along with some other improvements for better performance overall.
Head of WordPress, GoDaddy