If the domain scores are high across the board, you would expect the full scale IQ score (which takes all those areas into account) to be higher still. This is because it is unusual for someone to be globally strong in all areas.
It's a little hard to know what his full scale IQ would be since you are cobbling together the results from two different tests. The SB-IV has a standard deviation of 16, while the WPPSI-III has a standard deviation of 15, so the scores are not quite comparable. Also, the processing speed and working memory subtests were not administered.
You may want to wait until he's six and have him restested using the full WISC-IV or SB-V
My guesstimate would be that he is highly gifted. You could take a look at Dr. Ruf's book
5 Levels of Giftedness to get a qualitative description of the gifted spectrum. Here's an excerpt:
http://www.educationaloptions.com/resources/resources_levels_giftedness.php
