If I could know that my modems would not pass on IvP4 encapsulated IvP6 (Class A, B &C ) address then I would be more amenable to it BUT
Microsoft & others already have tunneling boasting of busting a hole thru NAT and identifying every little thing you have connected to your network.
This is as bad as Universal Plug & Play UPNP, letting anyone see the peripherals on your Computer.
IvP6 NAT or IvP6/4 NAT
So get up the hardware manufacturers to guarantee their gear can do that and that be one step in the right direction.