In the scheme of things, I would assume that the 'current system' is IPv4 since it is in widespread use and the primary system for addressing internet sites and services.
"IPv4 provides approximately 4.3 billion addresses; a subset of these have been distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each." - Wikipedia (
http://en.wikipedia.org/wiki/IPv4_address_exhaustion)
IPv4 can provide such a large amount of addresses due to the large number of combinations possible. An IP address is broken up into 'octets'. For example, the address 212.33.77.109 contains four octets (or sets of numbers). Each octet can reach a maximum of 255.
However, even though there are many addresses available, the last of the IPv4 addresses have been sold to ISP's and other organisations. This means that within a relatively short period of time, the addresses will soon run out.
IPv6 provides far more addresses than IPv4, hence why everyone will eventually need to switch to IPv6. This change however takes time, preparation and costs money. Within the near future, maybe 2-5 years, the entire world will most likely be running on IPv6.
