CentOS 6.0 has been released: http://wiki.centos.org/Manuals/ReleaseNotes/CentOS6.0
I believe I've heard no (future) Plesk 9.x release will support RHEL/CentOS 6.x, is that correct?
Since Plesk 10.3.0 supports RHEL 6, it should also work on CentOS 6, so I expect official support for Plesk...