It just will not happen. Many embedded devices build today don't even enable the IPv6 stack while it's only a configurable option away in the Linux kernel. And these devices aren't even released yet. They will after release run for a decade in the infrastructure. Sure we tell people who make them to care. Yet mostly they have more important things to care about, as for example to get them working in the first place.
An extra screen in the config box to set a static IPv6 address on an embedded device? Not seen one yet... Why? Because these embedded boxes are typically run in a seperate VLAN in the company.
Corporate requirements for IPv6 are close to nonexistent, so nobody cares, nor will.
It's not that I'm against IPv6, but one has to be realistic about what to expect from the rest of the world - and a drastic change without a game-changing urgent need is not one of these things.
And I'm still waiting for an example of any organization _ANY_ organization who needs to have in the order of 16 million directly communicating devices on their private network. Just a million will do as well.
Probably Google is the only organization which comes close to that order.
And even for them, there is not really an important reason why their infrastructure could not be split up between the google search cloud as one 10.x.x.x range and the gmail infrastructure as another one, for example, as direct communication between the two is probably unnecessary and managed by separate teams anyway.
One could argue that the 'renumbering' is difficult. Yet the cluster which Google build handles server failover, swap-in and swap-out and data partitioning as one of the major features. Fail to see why they couldn't implement it on the 'private IPv4'-level either...
While I agree that on their scale, such an experiment might be valid, my guess is that it will remain as such;... an experiment with a lot of problems:
1) increased latency because of IPv6 tunneling - and Google is very latency conscious
2) less proven technology leading to exotic problems which show up even more at the Google scale - because nobody uses it
And for what?
To solve the 'we are too lazy to write a stupid IPv4 pool re-numbering/re-partitioning'-problem? While it can be done with a very small shell script(TM)? ;)