It is short-sighted to insist that currently separate IP networks will never interoperate directly as part of the “BIG I” Internet.
Given the flux in corporate structures, functions, and ownership, anyone with at least an ounce of forward vision will design, construct and operate every network using globally unique IP addressing. This makes the boundary condition changes less traumatic, reduces renumbering expenses, and frees the network operators (NANOG-on-topic!) to manage their ever changing network in an efficient and cost-effective manner.
IPv6 is an obvious source of sufficient IP addresses to meet needs for the next decade or two. If there are certain problems with IPv6 allocations now, please offer constructive suggestions regarding corrections and improvements. NANOG may be a good forum for eventual input to ARIN, et alia.