The problem with determining when all 3.7B IPv4 addresses will be in use overlooks the fact that it becomes increasingly difficult to make progress.  As Christian Huitema pointed out in RFC-1715, each level of delegation will be unable to achieve perfect utilization of the address space so each must introduce a level of addressing inefficiency.  The distant end of this scenario would suggest going into each /24 network and ensuring all 254 addresses are actually being used; this seems at best unlikely.
	The pain level formula in this graph is –ln(% unallocated space).  This is designed to require fewer and fewer addresses to incur each additional unit of pain, becoming infinitely difficult to allocate the last IPv4 address.  Note that the right end of this graph is now in 2006 as compared to 2025 in the previous graphs.