Not exactly extended norms, but it appears that, as of March 2017, Linda Silverman and Susan Engi Raiford of Pearson have developed an Expanded General Ability Index ("Gifted Index"), which is somewhere between the old WISC-IV GAI and the new WISC-V GAI. It consists of the four subtests in the Verbal Expanded Crystallized Index (VECI) and the four in the Expanded Fluid Index (EFI), combined into an eight-subtest composite index. Unfortunately, I have not yet determined how anyone other than GDC can calculate this.

...pronounced like the long vowel and first letter of the alphabet...