That's factually incorrect. Perl 6 also known as Raku is an unrelated language. The latest version of Perl is 5.30.0 as shown on http://www.perl.org/.

Perl 6 is also Perl, but Perl 5 was the glue of the Internet with millions of lines of Perl 5 code written and still in use.

Perl 6 was a bit slow to start and has not seen wide adoption. With Python, Ruby, and now even Powershell as scripting competitors, people have more options and aren't choosing it as much.

Perl 5 was an easy choice when it was practically a standard part of LAMP stacks via mod_perl in the Apache web server. Now there are so many backend web server choices you can pretty much use any major programming language.

I don't think Perl 6 will displace Perl 5. Perl 5 may even out last Perl 6.

Really Perl 6 and Perl 5 are different languages. I think even maintainers see it as that, please correct me if I'm wrong. I believe there was a discussion about renaming Perl 6 to avoid this confusion.