The WISC-IV is still fine, though not preferred. It's been over a year since the WISC-V came out, so ideally, that would be better, but it's only just over a year. Primarily, the difference is one of norm obsolescence. WISC-IV norms are over a decade old now, while WISC-V norms came out in 2014. Using old norms tends to slightly inflate scores, with the Flynn effect (rising IQ scores over time) not quite as predictable with GT students.
The WISC-V also has a slightly different factor structure, with the main difference being that the nonverbal domain has been split out more clearly. The WISC-IV combines visual spatial and nonverbal reasoning into the same index, which sometimes obscures strength in one of those areas, if the other is not equally strong. The WISC-V separates them into the Visual Spatial Index and Fluid Reasoning Index. Students with motor or spatial deficits, but high abstract thinking, often benefit from having these domains separated.
