> By assuming an hierarchical internet where everybody but the tier 1 providers are single homed?
Actually the (completely unworkable) idea was that people who had multiple providers would simply have multiple IP addresses, and advertise all of them. That *possibly* could have even worked (with a lot of effort) if TCP supported multiple endpoints and transparently switched between them in real-time. But, it doesn't.
The one (pretty minor) remaining thing IPv6 does to help reduce routing-table size is reduce fragmentation of the address space -- a single organization at a single location is less likely to need multiple non-contiguous addresses spaces than in IPv4.