We are at least at the ISP I work for. That is a major project for us this year, but any network engineer can tell you that deploying IPv6 is not straight forward at the ISP level. Getting everyone together on how to have some standard form of addressing from different entities is the toughest lift. Get Juniper, Cisco, and Arista on the phone and you will get three different ways on how to deploy it. You don't want to be the odd duck once the dust settles.
You are correct on the ISP level. I am a network engineer for an ISP, we utilize Corero to monitor and mitigate DDoS attacks into our network. Since 99% of the time the DDoS is not targeted to us but rather the customer, I also kill the active IP addressing to their Modem/ONT, and configure that endpoint so it isn't allowed to pull an IP. Once the attack stops, re-config the endpoint and have it pull a new address.