It should be enough however companies like Microsoft have got big slabs of the pie early (i might be mistaken but that was my understanding). Also if we want to get every appliance in the house/garden on the net it might be pushing it, but is an average of 2.2*10^20 addresses per square centimetre overkill?
RE: Address assignment
[Taken from: http://www.ewos.be/coexist/etg071/ga ddress.htm ]
The Internet Assigned Numbers Authority (IANA) has the responsibility for the management of the IPv6 address space , with the advice of the Internet Architecture Board (IAB) and the Internet Engineering Steering Group (IESG).
Also from http://faq.v6.wide.ad.jp/Trans/4-22.html it mentions a paper that tells you how to allocate your own site local addresses