I find the argument that a PHP5.2/PHP5.3 switch is not a justifiable expense very short-sighted from cPanel.
From a hosting provider's point of view we have 2 options:
1. Use PHP5.3 and Lose customers who can't upgrade to PHP5.2
2. Use PHP5.2 and Lose customers who require PCI-DSS compliant hosting / require PHP5.3 for their software
Either way, we lose business.
The suggestion to play the server shuffle & keep moving clients around is a last resort option, but means extra hassle & clients who are asked to move servers, might take the opportunity to move away entirely.
I've seen quite a few hosting competitors of ours who provide a PHP5.2/PHP5.3 switch in their control panel, obviously they are not using cPanel
So bottom line is that hosting providers who trust in cPanel are left worse off than their competition, and either play a server shuffle or lose clients.