Scott Galloway also believes it will be in Washington, and was always intended to be: https://www.youtube.com/watch?v=_HyiY_m_YxI&t=542

I recommend watching the actual talk, but there are a few sections of it summarized (including a bit about Amazon HQ2) in this article: https://www.recode.net/2018/9/19/17878766/scott-galloway-pre...