ISPs have no competition, but Youtube, Facebook and Wikipedia do. The only thing those sites would do is shoot themselves in the foot while trying to force an immovable object to bend to their will.
Lobbying the FCC on the other hand, that could actually affect change. It would be in the best interest of everyone (excluding short term investors in the various ISPs), with networking equipment manufacturers poised to win the biggest.
I think it's all moot though, as Comcast is reportedly very far into their IPv6 rollout, as is Time Warner Cable (I have full dual stack at home with my TWC service). AT&T reportedly has rolled theirs out too, but some customers have experienced issues as the MTU setting is different on IPv6 as it is for IPv4. I also know first hand that Verizon Wireless runs dual stack over their LTE network.
At this point, I think it's really just getting the proper equipment in the hands of customers that is the hindrance.