The only solution is a gov't mandate. China went from almost no adoption to leading the world in adoption (77% of all Chinese internet users) in a few years because they explicitly prioritized it in their last 5-year-plan.

The ISPs aren't gonna do it on their own.

US government has finally learnt from how vendors break the mandates and there's now IPv6 mandate if you want to sell to federal government, and waivers are only available for buyers not vendors, and individually every time.