
NethServer 6.8 can be updated to 6.9 from the Software Center page and can receive CentOS 6.9 RPMs!
Check the mirror status here: http://www.nethserver.org/mirmon/
There had been only a dependency issue reported and it was blocking the update. It has been fixed and is available from the 6.9 tree.
More info:
Bug link:
http://dev.nethserver.org/issues/3439
See also the announcement from upstream: