But that's my point. People do understand how version numbering works. But Perl is trying to change that by saying that Perl 6 isn't the next major version of Perl - it's just another language in the Perl family. I think that just confuses people.
Personally, my guess is that once the performance issues with Perl6 have been solved and there's proper Perl5 and CPAN integration, the whole sister-language-instead-of-next-version thing will go away.