Those substitutes aren't anything more than a transitional mechanism. Dual stack is the way of the foreseeable future, I don;t see 100% only IPv6 as happening in the next 5-10 years (at least). Troubleshooting anything that traversed a 6to4 gateway? It's not a good time, even if you have control of said 6to4 gateway, and I can say that empirically. It's a far better strategy to roll dual stack wherever possible, even if that means forgoing things like QoS for the short term.
Anyone that has managed an IPv4 + Appletalk, IPX or other random protocol can understand that it's just another communication protocol on the wire. I started on networks that ran everything under the sun and, sure, it was more complex, but it wasn't abnormal. It was just the way it was.
What I am getting at is that if we can get more of us on board, we can get more features added and more gear supporting it. We are at the helm of the ship, we just have to steer it.