Will there be a 3.10 or go to 4.0 after 3.9, per one of his core developers?[1] It's hard to tell with Python's leadership (no intentional mockery of the term leadership).
My guess is that they'll indeed push onwards to Python4 as soon as possible. This being another attempt to make Python2 look as old and crufty as possible. "You're still on Python2? Wow, I'm on 4!". That's the type of political and psychological game the Python core dev team has been playing since 2008 with 3's release. Right alongside the 2020 EOL, another political move. Even though Python 2.7.'10' was never supposed to exist but they went back on that.
This because Python3 is mere technical churn, it is not true technical innovation.
The issue here is really one with the Python core development team. They have also adopted every niche feature into Python3 by whoever came along to ask for it.[2] This was done for the same reasons as the relative rush to rebrand the failed 3.x branch as 4. An attempt to stir up any hype possible for 3.0+.
They got so much wrong with Python3. Feature soup, unicode, and performance losses over 2. Unicode-by-default is the big deal and they didn't even get that right. They simply remapped unicode to str. Which for such a big breaking change, should've been UTF8 alongside other new languages such as Go.[3] But it's worse than that, Python3's feature soup continues in 3.6 there will likely be a 4th string formatting option[4] among throwing everything they can against the wall to see what sticks (while bloating the supposedly simple, "beginners" language).
While Python2 has been riding high in popularity[5], it has absolutely nothing to do with Python3. It's in spite of it.
There's good reason the core dev team "extended support" for 2.7. It's because they really did create a new, much less successful language and would've lost complete control of Python had they not done it.
Python3 is a language that looks mostly like Python, but is Python in name-only. Worse of all, it doesn't stand on it's own two feet with technical merits. I would personally recommend sticking with 2 until 3 ever makes sense, or finding something else to use like Swift or Go.
Unlike a web browser or another piece of software, the "latest version" of a programming language is not always in the end-user's best interests.
[0]https://twitter.com/gvanrossum/status/583346987925278720
[1]http://www.curiousefficiency.org/posts/2014/08/python-4000.h...
[2]http://learning-python.com/books/python-changes-2014-plus.ht...
[3]http://lucumr.pocoo.org/2014/5/12/everything-about-unicode/
[4]https://www.python.org/dev/peps/pep-0498/
[5]http://www.tiobe.com/index.php/content/paperinfo/tpci/index....