One of the discussion was on the Perl blogs[1]. Most of the devs there are Perl 5 devs and they also decided against the name change. Perl 6 is the next iteration of Perl that has been redesigned from the ground up. Why should it bare a different name? Yes, the redesign took more than a decade and it's incompatible with Perl 5, but so is Python 3.6 compared to 2.7, albeit to a lesser extent. Even Perl 5.26 has changed a lot since 5.6. In fact the least common denominator is 5.10.1. Using older versions is discouraged since they're largely unsupported by the majority of CPAN modules.

1. http://blogs.perl.org

It was a decision made by Larry Wall alone.Since it’s his language, he’s allowed to do that.