From my point of view, committing to any kind of "core" library now would throw Perl6 into the same (perceived) pit of backward compatibility friction that gets ascribed to Perl5. Perl5 has a working deprecation cycle now to solve that problem, but Perl5 is not within the dynamic zone of "let's try every crazy idea that we hear of".

Personally, I think Perl6 would do good to explicitly state its stance on parallelism and concurrency, so that libraries will get implemented relying either on sane userspace threads, coroutines or OS threads. Even better would be explicit language support for both, coroutines and (Userspace) threads. But then, I have both in Perl5 already, so I might just be biased here.