In addition, my estimates are based on experience. I work for a business-to-business ISP with many thousands of customers. The amount of those businesses that understand subnetting, VLANs or even IP addresses is tiny and near microscopic when it comes to residential customers. It’s great that you’re learning about networking, but you are one in a thousand. Even I can’t envision a realistic requirement today for multiple subnets in my home and I’m about as geeky as they come.

What becomes of IPv6 when we look 40 years down the line? There’s 7 billion people on earth today, and if each had a dozen /48′s as you say that would be 84 billion /48′s. By 2050 the population could be 11 billion by estimate. That’s 132 billion /48′s, which would put the total usage of earth at around /12. What if start colonizing other planets? Or introducing nano-size computers… thousands of tiny machines on the head of a pin each with it’s own IP address – imagine every pinhead needing a /48 to itself.

Why not just be conservative now and save ourselves problems down the road instead of making it our children’s problem? One of the best schemes I’ve heard of recently is to assign a /48 to each customer, but only configure a /64 from within that /48. That means that by default each customer has a /64 but can if needed be easily regraded up to a /48. If we have availability problems in future, the unused remainder of the /48′s can be divided up to service other customers.

First, the “waste” of IPv6 is not a bad think.
IPv6 ranges won’t miss, even if each human beeing on earth as a dozen of /48.

There is a choice to do between “many subnets for many users” and “many IPv6 for each users”. But the choice of a /48 per customer won’t be a trouble for the whole Internet. Think about the fact that plateforms who actually use hundred of IPv4 (let’s say, a big web hosting provider) could use a /48 for this too. So the total number of /48 should be less that the actual number of IPv4 needed.

Second, there can be geek in the middle of average customers. People deserve the right to become geeks, and their children deserve this right too.
I’ve started to discover the network with a very mainstream french ISP. And I have been able to do stuff like hosting my own server, because the connexion was enough “geek-friendly”: I had a public IPv4, it was possible to redirect ports on my connexion. From basic customer I slowly became a geek, and I’m sure that I am not the only one in this case.

So, let’s assume you provide a /64 per user. In a average family of basic users, one of the kid feels curious about network stuff. He will become to a point where he may need a /48 (let’s say a /56) to go deeper. How come will he get it, if he needs to ask his parents, if they have to pay, or give a reason, if this may need to break and re-do all the existing network of the “geek to be”, who may have set up a foobar::1 IPv6 on a home server and will need to change it because the new /48 doesn’t match on the elder /64?

Third, assuming that end-users won’t need many /64 is a bet. You and I cann’t guess how IPv6 and the “end to end” principle will be used. Domotic could need it. People may have friendly GUI to set up one /64 for their PC, with firewalling, and another /64 with smart devices (coffee maker, heater..) that would provide a remote control API from smartphones. Yes, one cann’t be sure this will happen, but you cann’t be sure this won’t.