- Python3 currently exists, and there is a large push to get the majority of the "big" packages to support it (many of which do currently support Python 2.x and Python3).
- It's possible for a Python package to support both Python 2.x and Python3 at the same time or to program the Python 2.x version in such a way that converters like 2to3 can do the conversion for you. I'm aware of no such tools or capabilities between Perl 5.x and Perl 6.
- Python3 isn't as ambitious as Perl 6 is/was.
Edit: As to point #2, I recall that there may have existed (maybe it still does?) some project to use Perl 6's "reprogram the grammar" capabilities to turn Perl 6 into Perl 5. I'm not sure how I really feel about that though. There was also a time when there was some buzz around Parrot VM[1] that was associated with Perl 6 (I don't know if it was some official partnership or just some announcement of Perl 6 support in Parrot).
Heck, apart from few - even those which are not supporting Py3k now have alternative package in PyPi. So it's positive sign.
When a loved platform stops evolving, as python2 has, there is this lovely period when it continues to be awesome, while requiring you to learn nothing new. Python is here now. But come the day that my new Linux distro links to 3 over 2, I will get organised to move.
I'm sad about this, I loved programming Perl a decade ago but the last side project I wrote in Perl was all the way back in 2010.
It was mostly new things, not different things. I don't even remember the new object model being that hard to pick from the PHP4 one. I think lots of developers got more stuck on the 5.2 -> 5.3 transition.
Isn't Python 2/3 more about libraries and compatibility than hosting ? My personal anecdote is that it deferred me way too long to learn the language seriously. I didn't want to waste time learning an old version but too much things were on it, especially Django and Flask (being mainly a webdev).
PHP7 vs Hack could mirror that though.