They're totally happy with renting out space that they paid (and pay) nothing for, for prices like 1 USD per month. Why would they help move to IPv6? Not happening. Short term solution to this is the obvious: force everyone not using their space to hand it over. What you can't use for 5 years into the future should just be handed back. Ban large ISPs from charging for IPv4 addresses to their downlinks.
This is my personal Mastodon.