I can tell you this: the only scalable solutions on the horizon are:
- moving multihoming related state out of the DFZ (this is what shim6 does)
This is what geo-topological addressing does.
- remove the requirement that every DFZ router carries every prefix, which can't be done as long as PI blocks sit at the top of the addressing hierarchy
Geotop addressing does this also because only a few aggregates are in the DFZ. The detail is elsewhere.
The closest thing to a magic, pain-free solution would be to allocate PI blocks such that it's possible to aggregate them together and ignore the more specifics for far away regions of the world, so that in 2030 you don't have to carry 60000 Chinese PI blocks world wide that all sit behind the same Great Firewall anyway,
Exactly! And this doesn't need to be done in a mandatory way. It can be done so that large providers can continue to use provider-aggregatable addresses. Geotop addressing is one of those 80-20 solutions where the largest 20% of providers mostly use classic IPv6 address but the other 80% of smaller multihomers use geotopologically aggregatable addresses. --Michael Dillon