What criteria would a language (any language) have to fulfill so that you would call it the next version of Perl?
For starters, it should be (largely) backwards compatible. For instance, the majority of CPAN code (just to take an example) should run without any problems or differences. That's not true with Perl 6. Operators change names. Sigils change. The regexp syntax is quite different. For loops change. Hash indices change. There'll be syntax changing whitespace. And no doubt there'll be more, but I don't look that often into Perl 6.
Now, noone has to defend the choices that were made. That's not the point. But I cannot take a Perl 5 program, and gradually add Perl 6 constructs (I'm aware of the plans to be ablet to compile Perl 5 - but that's not backwards compatible - then Perl 5 could be called backwards compatible with sh, because it's able to fire up sh for you).
There are too many syntax changes to make it backwards compatible in my book.
Note that I'm not saying 100% backwards compatability should always be achieved. But IMO, the changes with Perl are too much that I won't call "Perl 6" the same language as "Perl".