WPA is a subset of the IEEE’s more complete 802.11i security standard, which remains some 15 months away from certification and may require changes in hardware. The Wireless Ethernet Alliance decided to support WPA with a certification program partly because its members did not want to wait so long for a fix to vulnerabilities in Wired Equivalent Privacy (WEP), the existing Wi-Fi security algorithm. Also, members wanted a security upgrade that a software upgrade could in most cases provide.
It looks like this is a decent compromise until 802.11i gets rolled out. Good to know though.