http://blogs.perl.org/users/alberto_simoes/2011/06/perl-perl...
http://www.modernperlbooks.com/mt/2011/06/perl-perl-5-perl-6...
http://blogs.perl.org/users/mithaldu/2011/06/why-are-people-...
http://jjnapiorkowski.typepad.com/modern-perl/2011/06/perl-5...
Few people outside the perl community see "Perl 5" and "Perl 6". For most people referring to the language they simply call it "Perl."
For marketing to developers specifically, I think the biggest hurdle isn't the name but the stigma attached to the language. Most developers I talk to outside of the perl community still see perl as a "write only language" that consists purely of "line noise." They don't specifically say whether they are talking about Perl 5 or Perl 6. To them there is no distinction.
Nobody want's to invest time into learning something called "Perl 5" when there's something already out there called "Perl 6". Yes, some research into it will reveal that they are now on two separate dev paths, but there is still some mental stigma associated with investing time in learning an "old version" of something. And learning the "newer version" quickly reveals that it is not widely used/supported yet. They are basically two separate languages and should be treated as such.
These days the arena Perl competes in is extremely competitive, and these seemingly small issues will continue to be disastrous for Perl.