Actually, in the default kickstart for redhat, we've a "yum upgrade" in the middle of the file.
I think it is wrong to put "upgrade" because it will defintively upgrade the current install to the last release. In case I want to install Centos / Redhat 5.4, I don't want the installation process automatically upgrade it to 5.6

That's why I think that you should modify the template with "yum update" instead of "yum upgrade". That would keep the current selected release updated !

Thanks