In 11.1 and 11.2 CORE Generator, the Virtex-4 RocketIO Wizard does not appear in either the View by Function or View by Name tabs. This Answer Record discusses how to select and generate the Virtex-4 RocketIO Wizard.
At the bottom of the CORE Generator window is a check box titled "All IP Versions". Once you select that check box, the LOGICore RocketIO Wizard should be selectable for Virtex-4 projects. v1.6 is the most current version, and this is simply an issue in CORE Generator, not the Wizard, and will be corrected in a future version of the software.