<quote name="Moritz Muhlenhoff" date="2015-07-21" time="10:44:59 +0200">
Debian 6.0 is supported until February 2016 and has PHP 5.3.3
Ubuntu 12.04 is supported until April 2017 and has PHP 5.3.10
RHEL 6/Centos is supported until June 2017 (and limited supported until 2020) and has PHP 5.3.3 (but they also provide officially supported 5.4/5.5 packages)
Based on those dates I think we should make the bump sooner than later. Less than a year left for Debian support isn't that long, really.