Neel Kashkari of the Minnesota Federal Reserve is an inflation dove (man after my own heart). He is focused on the long term expectation of interest rates. Cash rates aren't as important as the long term expectations and if cash rates are not as influential in driving expectations, the policy such as forward guidance may be more important. As the Fed removed accommodation, inflationary expectations fell. End of QE remove the assumption of extraordinary measures supporting the economy. Neel argues this was far too hawkish. I would push back and say that this wasn't too hawkish but there was nothing the Fed could do.
Not denying what a fantastic investor that Jeff Gundlach is but just because he say someone will be the Fed chair, doesn't make it so. He has no more an edge in determining who will be in the seat as the rest of us. It is an opaque, political process and given President Trump's tendency for unconventional thinking, it could be anyone.