Ipv6 should be the way to go nowadays, no ? For sensors network, people are using ipv6: as you don't have enough ipv4 adresses for computers and phones, you don't use ipv4 for sensors networks and IOT, that's a nonsense.
I would imagine almost all IoT devices in the home are using IPv4 at the moment, you can’t rely on IPv6 working properly with many ISPs. They don’t have to use public addresses, so scarcity isn’t a problem.