I was thinking that, too.
The oldest computer I have around is a 1990 Amiga 500; I mostly use new kit, of course. Anyone who gets an implant is going to be stuck with it pretty much for life, or commit to brain surgery every 3-5 years to install the newer one.
On the other hand, a 'trode net or hat would seem doable; sign me up for that.
Forcing the holders of large legacy allocations to give them up would hurt more than moving to IPv6, and it'd only get us a few more years of IPv4 growth. Opening up the class-E space would also hurt more than moving to IPv6, and still only give us a few more years.
NAT effectively adds 16 more bits to the address, but does so on a per-connection basis, not a per-node basis. It requires the network to be stateful, instead of just passing packets while the end hosts carry all the state. (This means that the end hosts can't just route around problems.) NAT is messy, but it happens to work because it can steal some bits of TCP or UDP to make up for not having enough in the IP header.
IPv6 adds way more address space than anyone can think of a use for. So it can encode a lot of information about the node's position in the network, plus keep an address unique for (practically) ever.
300,000 Americans is a big N.
"my terminal is a lethal teaspoon." -- Patricia O Tuama