WEP2 was a short-lived extension to Wired Equivalent Privacy (WEP), a wireless network security protocol that was widely in use (and still is) but was found to be inherently flawed. The goal of WEP2 was to buy some time before WEP was replaced by something better (turned out to be Wi-Fi Protected Access, and then WPA2). WEP2 extended the IV and key values to 128 bits in an effort to fight against brute force attacks and duplicate IV deficiency (this change was kept in WPA's TKIP).
WEP2 might have been useful for a while for hardware that could not be upgraded via firmware to support WPA or WPA2 instead, but unfortunately the WEP flaws went deeper than expected. More work would have been needed on top of the changes made by WEP2 and so the name and algorithm were dropped, and the industry moved toward WPA and WPA2 instead. WEPplus was also an enhancement made to WEP that attempted to address the security flaws.
More information: Wired Equivalent Privacy (WEP)