Elizabeth Naramore, host of the "Future of PHP" webcast series for EngineYard has put out a call for PHP internals developers inviting ones that would like to chat a bit.

Consider this a call to the PHP Internals team. We've been doing a series of panel discussions over at Engine Yard about PHP-related frameworks and where they are going in the future, but one important piece that's missing is the discussion about the future of the PHP core. [...] If you're a core PHP contributor and you want to voice your opinion in a friendly panel discussion about where you'd like to see PHP in 5 years, then I'd love to chat with you and include you in the discussion.

So, if you've worked on the internals of the language and would like to be in on the discussion, let Elizabeth know by dropping her an email that you're interested!