> 3. History has shown that upgrading network backbone hardware (in particular) is incredibly difficult through a process that's been described as "ossification", which is a nice description. Basically, network relays and routers wanted to avoid security issues and decided to discard things they didn't understand.

What makes you suggest that it's backbone hardware that is the problem? It's largely enterprise customers and tier 3 providers that don't really do IPv6 afaics.