This will depend on whether or not he's suitable for the job. It is still not defined whether we're following that approach. It is still not defined whether we're following that approach or not. It is still not defined whether or not we're following that approach. "Or not" doesn't really seem to be needed to complement "whether". More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.