Most people don't believe that Perl 6 is "the next version of Perl".

That's what many people say, but when I engage them in discussion I find that what many people actually mean is

Perl 6 is not the next version of Perl 5

Which is right, of course.

In some ways Perl 6 is quite different from previous Perl versions: it breaks backwards compatibility, is developed in a different mode (specification and test suite first, multiple implementations possible), has a slightly different syntax.

But what makes a language Perl? It's only partly the syntax; it's mostly the principles behind the language: DWIM, whipuptitude, TIMTOWTDI, (limited) correspondence with natural language and so on. I've written about that before.

Still I can see why many Perl 5 programmers fear the "Perl6 is the next Perl version" statement, and deny it because they fear it: It's not yet near wide spread adoption, there's no clear migration path, it's not backwards compatible, etc. That's why it's important to communicate clearly that it's not the same situation as with gcc, for example: Users of gcc-$version will eventually have to upgrade to gcc-$higher_version, because gcc-$version will stop being maintained, and thus not being ported to modern CPU architectures, libc version etc.

I don't see that risk for Perl 5 any time within the coming decade: Even when we'll have a Perl 6 compiler that is fast, stable and portable, and implements a sexy Perl version, tons of software and libraries will keep Perl 5 alive. And of course the stubborn programmers that just love Perl 5, and will continue to love it even if "the next major version" is there.