Why not a /48 for all? IPv6 address space is probably cheap enough that
even just the time cost of dealing with the occasional justification
for moving from a /56 to a /48 might be more expensive than just giving
everybody a /48 from the outset. Then there's the op-ex cost of
dealing with two end-site prefix lengths - not a big cost, but a
constant additional cost none the less.
And let's not ignore the on-going cost of table-bloat. If you provide a
/48 to everyone, in 5 years, those allocations may/may not look stupid. :)
Right now, we might say "wow, 256 subnets for a single end-user...
hogwash!" and in years to come, "wow, only 256 subnets... what were we
thinking!?"
Its up to the ISP or LIR with minimum recommendations.
"RIRs/NIRs are not concerned about which address size an LIR/ISP
actually assigns. Accordingly, RIRs/NIRs will not request the detailed
information on IPv6 user networks as they did in IPv4, except for the
cases described in Section 6.4.4 and for the purposes of measuring
utilization as defined in this document."
:)
Deepak