Hello all,
as I read in the actuall Debian-news-email, the debian-project plans to remove php4 from testing and unstable in the future [1]. Because hemlock runs testing, php4 will be removed then too.
I have no idea, how long that take (normaly, debian is more slow). So if one (or more) of your tools use php4 still, this is a good timestamp to port it to php5.
Sincerly, DaB.
[1] http://www.us.debian.org/News/weekly/2007/06/index.en.html