1.) python3 will die (long live python 2.x)
2.) python3 will become easier to port to
If neither of those happen, python itself will probably die in the long term, so I'm pretty confident one or the other will come to be.
It doesn't matter if OS/2 the best OS out there - it's dead. Same with Python 2 - who gives a rats whether it is good, better or best, it's dead technology.
On the other hand, companies that are providing SDK's or libraries to interface to their systems have an absolute obligation to provide their code in Python 2 and 3.
Dogmatically sticking to Python 2 is entirely valid for internal systems, but what the heck is the point of providing interfacing code/SDKs/libraries if it does not interface? Google is welcome to keep all its internal systems on Python 2, but all its SDKs should support Python 3. And all Google's public facing developer tools should support Python 3 - nothing else makes sense.
In terms of porting, plenty of people seem to have done it - here's the list: http://python3wos.appspot.com/
Why did you state this as if it were a self-evident fact? There are seemingly clear reasons why this belief is completely absurd.