This is inspired from last night's LOPSA DC meeting. The topic was IPv6 and we had a round-table.
One of the big questions brought up was, "What's making me go IPv6?"
The stock answer to that is, "IPv4 addresses are running out, we'll have to learn at some point or be left behind."
That's all well and good, but for us? Most of us are working in, for, or with the US Government, an entity that is not going to be experiencing v4 address scarcity any time soon. What is going to push us to go v6 (other than the already existing mandate to have support that is)?
In my opinion, it'll come from the edges. IPv6 is a natural choice for rapidly expanding networks such as wireless networks, and extremely large networks like Comcast/Verizon run for their kit. These are two areas where sysadmins in general don't deal with much at all (VPN and mobile-access being the two major exceptions).
If your phone has an IPv6 address and accesses the IPv4 internet through a carrier-grade NAT device, you may never notice. Joe Average User is going to be even less likely to notice so long as that widget just works. Once v6 is in the hands of the "I don't care how it works so long as it works" masses, it'll start becoming our problem.
Once having a native v6 site means slightly better perceived mobile performance (those DNS lookups do cause a bit of latency you know), you can guarantee that hungry startups are going to start pushing v6 from launch. Once that ecosystem develops it'll start dragging the entrenched legacy stuff (the, er, government) along with it. Some agency sites are very sensitive to performance perception and will adapt early. Others only put their data online because they were told to and will only move when the pain gets to be too much.
Business-to-business links (or those between .gov agencies, and their .com suppliers) will likely stay v4 for a very, very long time. Those will also be subject to pain-based mitigation strategies.
But the emergence of v6 on mobile will likely push a lot of us to get v6 to at least our edges. Internal use may be long time coming, but it'll show up at all because of the need to connect with others.