Perl6 was a reaction to Perl's loss of mindshare, not its cause.
One can speculate what might have happened if focus had been put on evolving Perl5, or getting Rakudo production-ready as-is instead of going through yet another round of 'tinkering' (eg making the compiler backend-independent, the New Object Model refactor, creation of MoarVM, the Great List Refactor, ...) - however my crystal ball seems to be broken and just continues to display 42 no matter the question...
You mean, 1.0 of the spec was released then. Don't pretend it wasn't perfectly possible to write and run useful Perl6 programs for a good ten years prior.
For some definition of 'perl6'. I have a perl6 book from o'reilly from 2006, and I flipped through it recently. It bears almost no resemblance to modern perl6. There were a couple of things that were still the same (and not just vestiges from perl5 like sigils and function calls looking like function calls), but by and large it was something completely different.
And today Perl is declining but still in serious use.
It's percentage has dropped by a significant amount, but I would bet the amount of new code has not dropped nearly as much.
Also I'm fairly certain that Go is close to a 10 year reaction to Python. (If not it's implementation.) The only difference is that it wasn't done in public. It's so much easier to ignore the years of development when you can hide it.
In my opinion a lot. I got my first job in 2003 programming Perl 5 and the way it was talked about, it sounded like Perl 6 was just a year or two away.
It seemed like so much of the web ran on it in the late 90s and early 2000s that it would have at least as much traction as PHP does today.