What Happened to IPv5, IPv7, IPv8 and IPv9?
The IPv4 market has created serious interest in the protocol far beyond the natural confines of networking professionals. These assets are worth a lot. Marketplaces, IPv4.Global's especially, have grown to be large centers of asset transfer by buyers and sellers of IPv4 addresses. IPv4.Global has helped transfer over $1 billion in IPv4 blocks.
Source: circleid.com