I actually think that what will really drive IPv6 adoption is if the price of IPv4 space continues its upward trajectory unabated. The price has about doubled at auction in the last year.
How are those two things related?
1. There are a ton of owners sitting on inefficiently used IP space.
Any company (not doing cloud hosting or network transit) that's holding a /8 is almost certainly using it very inefficiently, but an owner like Apple will never feel financial pressure to optimize or sell their /8. However, an owner like the university I went to (with a /16 network currently worth $3 million) will eventually face internal pressure to sell that network when the value rises to say $50 million.
As another example, Yahoo is currently announcing subnets containing 4.3 million IPv4 addresses, which is worth $193.5mm at auction. If the price of IPv4 addresses increased by say 10x, their IPv4 space would probably comprise the bulk of the company's value.
2. Owners will need to adopt IPv6 in order to realize these financial gains.
In order to sell a significant portion of their IPv4 space, an owner will have to compact their IPv4 usage into a much smaller space and migrate everything else to IPv6. This will be a huge undertaking for a lot of these places, but at some point it's worth it. By doing that, IPv6 adoption increases.
There is the potential for a feedback loop to be created where demand for IPv4 drops and the prices decline and so fewer conversions are done, but I tend to believe that IPv4 pricing will remain inelastic.
So basically the invisible hand of the market may guide us to IPv6, but I highly highly doubt we will have seen the last of IPv4 even decades from now.