@terry: take a look at
http://php.net/releases/. As you can see, the last 5.2.x version is from Jan-2011. So even if some OS distros maintain older versions for some time, I doubt that this one is still maintained anywhere.
Could not find a concrete roadmap, but the 5.6 and 5.5 branches should do it.
But I am quite sure you will get trouble with the several domains there when you upgrade PHP. I suggest a step by step migration to a newer server, migrating and testing single sites. A lot of work. Start with the MODX sites
On the other hand, keeping sites on old versions can make trouble too - think of Piwik which does no longer support 5.3.x versions...