There are tons and tons of hosts that still haven't upgraded to 5.3 - if the change comes in 5.5 or 6, it'll easily be 3+ years before it starts to be an issue.
I know for a fact that my old employer has one client who's still running 4.0, unless they've decided to pay out the ass to upgrade their spaghetti-coded system.
Considering that a) no out-ass money has been offered me, and b) I'm effectively the only person who could even fix bugs in the system, they're still running 4.0.
Reminds me of some places I've worked in my time. Clients made one site and wouldn't pay for an upgrade, and the folks running the company learned PHP when version 5 was brand new, and never wanted to upgrade because of a combination of clients not willing to pay and "seeing no need to upgrade".
Most of them are amazingly still in business, and their clients sites are still amazingly vulnerable. And we wonder why PHP has such a bad rep.
Sad but true. I love PHP, but it's like the Internet Explorer of (web-)server side languages. First there was the ordeal of dragging folks off 3 and onto 4, then 4 to 5, now 5.2 to 5.3 ... I look forward to writing PHP 6 code in my hovercar ;-)
