I know this isn't exactly what you were asking, but my company is using IPv6 internally for as many elements of our network as possible. We have a network with 10s of thousands of "devices" scattered all over the country, each of which has multiple IP interfaces (not PCs or Tablets, but machines). We can't use NAT internally as they all need to be directly addressable. They are not "internet accessible", but with the allocation inefficiencies of rational subletting we actually exhausted an entire "private" class-A (10.x.x.x).
Using IPv6 saved our butt - though it took a lot of arm twisting to get all of our key equipment vendors onto the bandwagon. At this point we are 90% IPv6 for these network elements.
For general Internet usage, IPv4 (nat'd) will be here for a very, very long time. Much longer than the "two years" stated above.