In my personal opinion I don't think ipv4 will truly be abandoned in my lifetime at-least. There's too much invested into it. RFC 1918 address space is still very useful for internal management of systems even in a dual stack v4/v6 environment. I can see ipv4 becoming less important in the near future, but it's not going to magically disappear. It sure would be nice to free up that CAM space being used on our routers for v4 though.