I was asked by my employer in 2003 when IPv6 would replace IPv4? After substantial research, my answer was, "never"!!! I almost got fired for that answer but I am correct so far.
There are a large class of people out there who do not understand the end to end argument in system design and who never saw a piece of bloatware they didn't love. For them IPv6 will happen tomorrow. They are to internet like maga people are to democracy - caustic.
In 2004 IPv6 was hyped as solving the impending IPv4 address shortage. NAT had already been invented and there was no shortage as IPv4 addresses were allocated as inefficiently as possible and there was no market to buy and sell IP addresses nor was there any rental cost for owning ipv4 addresses. So it was solving a non problem.
My employer Qualcomm eventually proposed using IPv6 for cell phone handsets in an overlay network called openran. This was a convenience and not a necessity because there are more than 4 billion cell phones in the world.
You just don't need these bloated addresses in IPv6. You need banks of addresses mainly for the server. The client never needs 65,000 incoming or outgoing connections. The number of client computers in the world that are running as servers and that need open datagram accessibility from anywhere in the internet is virtually zero. Want it? yes! Need it - meaning impossible to do without it - No! There are always bridging workarounds to avoid giving client machines dedicated IP addresses!
IPv6 is not respectful of small system design and hardly provides usable improvements to IPv4. IPv6 was a marketing tool invented by Cisco to sell bigger more expensive routers, not to solve a problem with any economy ... It is especially detrimental to IOT.