As a lot of people have noticed Oracle is offering a “conversion” script to move from Centos to Oracle Linux. Of course it is not really a conversion, it only moves the yum repos from Centos to Oracle. The existing packages are not touched. If you want a complete conversion have a look at my page about moving from Centos to Scientific Linux. You could use the same mechanism to move from any RHEL-based system to any other RHEL-based system.
I checked the announcement mails for the last kernel update RHSA-2012:1156-01. Here the recieved time for the mail on my mailserver.
RedHat: 14 Aug 2012 20:25:42 +0200 (CEST)
Centos: 15 Aug 2012 06:26:25 +0200 (CEST)
SL: 15 Aug 2012 16:36:55 +0200 (CEST)
Oracle: 15 Aug 2012 22:10:25 +0200 (CEST)
With this information in mind this Graph looks “interesting”.
But overall I like the idea that nowadays we are talking about hours of delay instead of days or weeks between Red Hat and the Clones.