The release schedule will slow down somewhat now that there are 2 different versions, PHP and PERL.
Basically the development will go something like this. Right now PHP 5.1.x is in the bug fixing stage. While this is going on 5.2 for PERL is being developed. Once 5.2 PERL is released then it will go into the bug fixing stage while the new features are being ported over to PHP. This will allow each version to have a good bug testing/fixing period while still having a good consistent release schedule.