@Lindsay - Well, it's not like this changeover to PHP 5 or above is going to happen overnight. It's a gradual change with 2.9 having the nag screen and more so when 3.0 comes around. Perhaps when the page is created in the Codex, I'll publish a follow up article letting you know but I'd imagine percentages based on what they know will be published in that page.

Most Webhosting companies are setting up to allow you to switch from PHP 4 to 5 or they might have upgraded the PHP behind the scenes which is what has happened with my webhost. If your webhost is stuck using PHP 4, I highly suggest submitting a trouble ticket asking them if they could upgrade their version of PHP and if not, explain the reasons why as it makes no sense unless the majority of their customer base is using PHP 4 based scripts.

No need to freak out right now as there is still plenty of time left before the switch.