Adding one more data- my son had IQ tests every year starting 3 till 6 by the same educational psychologist. He was tested on the WPPSI-III at age 3,4 and 5. Then the psychologist switched to the WISC-IV as soon as he turned 6. He took the WISC-IV at 6.2 and it went fine. In fact, his score on the WISC-IV was much higher.
You might want to switch to the SBV if you test him again. The recommendation is to not use the same test more than once a year, and in the case of HG children more like every two years. Otherwise they learn the test and this can skew your results.
