As far as I know, thanks to Module::Compile, you'll be able to use Perl 5 modules with Perl 6, so essentially you can have half of the code in Perl 6 and some legacy code in Perl 5 in the coming years...

Update: This is possible without Perl 6 carrying a lot of legacy cruft, so essentially you're getting the best from both worlds. Also, sixpan is on it's way and currently CPAN has a section for Perl 6 modules already.