According to the newly posted App Engine Product Roadmap, there are plans to add “support for a new runtime language.” In an email to the Google Apps Small Business Solution Providers mailing list Google had this to say:
“Of particular interest, may be payment for additional resource usage and a new runtime language – I can’t say what this language is, but you can probably guess if you’ve been following along with community demand.”
Looking at the issue list, support for Java is the most requested item followed by support for PHP, Ruby, then Perl. If you haven’t already, please go star the “support for PHP” issue (please don’t comment on it as it will email everyone who has already starred it – just star it!). Of course, I’m hoping Zend Framework is the framework of choice for all the App Engine specific APIs as well.