Given that P6 will be written on top of Parrot, it's likely that many of the modules you use won't be written in Perl. Instead, they will be written in other languages, like Ruby or Python or Java. So, they won't be in the Perl core. This is a "Good Thing"™.

I'm already looking forward to writing in Haskell, using Perl's proven ability to read/write a bazillion file formats, while riding Ruby-on-Rails on top of a Java GUI.

Seamlessly.