Let's assume a modestly sized Python program uses 8 libraries or so. Assuming 80% of libraries are ported, that means 20% aren't. The likelihood of at least one of your 8 libraries not being ported is 1 - (0.8)^8 = 83%. In other words, most people will find that at least one of their cricitcal libraries is not ported. That is certainly the case for me (Bloomberg Python API, for 2.7, and which, btw, only came out 6 months ago). Inevitably the people using Python come from specific domains, and use at least one domain specific library, so while all the common "usual suspect" libraries are ported, there is usually a very high chance that one critical library is not.
Perhaps the way the entire question should be thought of is: are there actually many properly useful Python 3 libraries that are not available in Python 2?? I bet the above equation would look much better when inverted.
The OP did not say it would "kill" Python, just that it would cripple it. Personally with bloomberg bringing out a Python2.7 financial module first, no 3.x support, the entire financial world is now also poised to stay on 2.7. That's a classic example: bloomberg only published this Python binding 6 months ago! no Python 3.0 for them.
I was referring to the title : "Python 3 is killing Python"
Anyway, it's a well known fact that 2to3 switch has tremendous inertia. Space, Medical, Finance are few of the applications where often old is gold (tried & trusted). What bloomberg did was logical, no surprise there. That decision adds little value to how Python 3 is impacting the growth of Python.
It is tremendously detrimental when a deprecated technology has all the inertia, because it is a dead end thanks to the Python bosses refusing to move it forward. Every new package for 2.7 (and no this is not old gold - this is a brand new library for access to Bloomberg's massive and uber-valuable database), every new package that invites more people into a dead end, encourages those people to look much wider (beyond Python) when needing to upgrade. Python 3 may be growing in absolute terms, but in relative terms it's a absolute dog compared with its competitors, including Python 2. Python 3 in its current form is doing everybody a huge disservice.
I see what you mean now on old is gold and yes I agree. Corporations love old proven tech for all the obvious reasons. Not officially deprecated but that's just semantics. The underlying point is that the Python leaders are trying to turn a superhighway into a dead end, and force a long and winding detour for most people onto another highway which is only marginally better. Being forced to take that detour simply encourages the exploration of other alternatives as well. By the way if they really had balls, they would've killed Python 2.7 in 18 months. Not 5 years. Force the choice. Clearly they themselves are not confident enough in 3.
Perhaps the way the entire question should be thought of is: are there actually many properly useful Python 3 libraries that are not available in Python 2?? I bet the above equation would look much better when inverted.