The four administrative groups like ICANN, NRO, IAB, and Internet Security declared that the IPv4 has drained out and the last two blocks has been allocated to RIR, and other last five blocks containing 16 million addresses might exhaust by September 2011. The switch over of IP addresses from version 4 to version 6 which has billions of addresses comparitively trillion times larger than 4.3 billion adrresses which IPv4 would support might have some security problems, as IPv6 has infinite number of namespace for addresses rounding approximately to 350 undecillion possible addresses.
The IPv6 is of eight sets of four digit numbers which are represented as 2^128/ 3.4 * 10^38 possible unique addresses. This is not yet widely adopted a World IPv6 Day is being planned so as the government and companies can test the technology, and for this switch over upgradation of equipments are needed like modems, hubs, etc., need to check their firewall to check how the new version can be handled since IPv6 come with optional extension headers which simplify the overall structure for improving the performance, also dual stack systems can be opted for managing both IPv4 and IPv6.