[azernik]

For preparing your applications for the eventual flip-the-switch transition; pay particular attention to sections 4.2, which describes a strategy (supported by Linux) for handing off the grunt-work of dual-stack to the kernel while making your userspace code only speak IPv6: https://tools.ietf.org/html/rfc4038

For a quick overview of the process of making your infrastructure dual-stack (with an aim to eventually phase out IPv4); note that most of the burden is on your networking-equipment vendor to make this work, unless you make your layer-3 equipment in-house. So it's mostly a deployment challenge, rather than a development challenge. http://www.networkworld.com/article/2285078/tech-primers/ipv...

If I might recommend a good tunnel broker for allowing you to deploy IPv6 internally and get connectivity to the global v6 internet even without ISP support, take a look at Hurricane Electric.