what icebraining said: use a nat64+dns64 at the edge of your network and make all your endpoints ipv6 only.
If you're an ISP, you could probably put multiple nat64 boxes in the core so that all your customers benefit from it and can gradually switch ipv4 off (since they can transparently reach ipv4 endpoints through the nat64 gateway).
Then there are a few applications that don't handle ipv6 properly (i.e. skype), and Apple's decision of mandating ipv6 support is meant to fix just that.
Then there is 4XLAT, ds-lite and others which allow for a single stack ipv6 network and carry ipv4 on top of it to the endpoints which need it.
If you're an ISP, you could probably put multiple nat64 boxes in the core so that all your customers benefit from it and can gradually switch ipv4 off (since they can transparently reach ipv4 endpoints through the nat64 gateway).
Then there are a few applications that don't handle ipv6 properly (i.e. skype), and Apple's decision of mandating ipv6 support is meant to fix just that.
Then there is 4XLAT, ds-lite and others which allow for a single stack ipv6 network and carry ipv4 on top of it to the endpoints which need it.