BlueHost and Hostmonster, the best web hosting listed on my site, has upgraded their 750 servers 2 weeks ago.
They are forcing all their clients to run Php 5 as default interpreter while keeping Php 4 as an option when Cpanel forcing their user to upgrade to the newer version
Apache has been upgraded to version 2.2.6 from Apache 1.3.x and MySQL upgraded to version 5.2.5.
PHP 4 is being deprecated and I believe more and more host will do similar upgrade very soon.