Answered on Quora.
The people around Langan in the extreme High IQ societies and groups (IQ = 160+) have been involved in not necessarily writing better IQ tests but in trying to write IQ tests that will specifically test for IQ’s in the 160–200 range, since most IQ tests top out at 160, and some top out even lower than that.
The problem is getting good validity for these tests, as the number of people with IQ’s this high is very small, and you need a large group to get good validity. So in a scientific sense it is a bit of a hopeless endeavor, but nevertheless, I think they should be able to write some good tests that measure extremely high IQ’s better than anything we have now. In fact, the group claims that some of its new tests measure very high IQ’s very well, but that’s them plugging their own. I am inclined to believe them though. They’re very smart people, and they would not lie about something like this.
