I expect a Perl::Lite dialect to arise (perhaps even using Parrot) if the changes in Perl6 will make Perl less good at what it's supposed to be good at.
The Winamp-ish reaction - people keep using Perl5 - is more likely I think.
Actually they no doubt will, regardless of how good Perl6 is, because there's so much Perl5 code still floating around. And then, most new things in Perl6 will be quite optional anyway so basically it can be used as a lite version of itself.
Uhm.. wait, I was trying to make a completely different point than what I ended up with. I guess my conclusion is it's not likely for Perl6 to not get adopted at all. Heh.
Makeshifts last the longest.