I'm not sure I understand your question (or perhaps I didn't phrase my comment clearly).
One of CentOS's strong points is that they do not continually update RPM packages with the "latest and greatest" release. It's all about maintaining a stable environment. (Ref: CentOS FAQ)
This is a very different environment than bleeding-edge releases, such as Fedora (the upstream version of Red Hat) which updates every year.
Combining a 10 year support cycle, along with focusing on stability, is a very strong selling point and is probably why CentOS is in the top 10 for server distros.
I'm not a fan of any particular OS. My point is that you need to support the major OS releases, as the decision to update software is not a trivial one. VSE's list of "popular server software" makes this point clear.
Decide if the features on 3.2 warrant breaking the earlier PHP releases and proceed from there.