There are a lot of changes needed, especially in (old) corporate environments.
I do use ipv6 at home, and at some of our customers, but some of them would have to essentially redesign their entire networking/vpn/security plan (and yes, existing ones are not good, split horizon DNS is almost always present, DHCP is not only used for security, but also for provisioning, there are products that scan subnets and provide reports on devices required for various compliances ...). And that is a hard sell, for what they see as next to no benefits.
The only major change is that instead of the smallest routeable unit being a single address the smallest unit is now a whole 64 bit subnet so hosts have a bunch of bits they can use for various purposes. Network administrators don't have to worry about that for the most part, the hosts figure that out on their own.
I guess there might be a security implication if someone has built their security system around knowing everything on the network via DHCP. But that was always a mistake. If you want real security you need to use 802.1x or similar. Being told you can't use DHCP to secure your network anymore is probably shock to some admins, but hopefully they take the opportunity to reconsider their system from the ground up.