I think it'll happen between election cycles. Trump and Hillary are both widely hated, and neither of them is going to do much good. The bubble is gonna pop, maybe accompanied by another major recession(maybe not directly in the US, but a bad enough recession in Europe will still cause major problems), and people are going to get mad. Already, most people know that the political system does nothing for us. It will just be more and more evident. The real question is, will it be France 1968 or Russia 1917(February, of course)?
The rush out of the coastal states is going to be a tsunami of people who have been saying 'fuck the flyover states' for a generation. Then they are going to realize that a huge tract of the nation where people can actually afford to live don't want a ton of SV and Brooklyn rejects. I remember reading people in Portland, OR whining about all the dan Californians moving north. The next migration is going to make that look like a holiday weekend.
Or currently: the people in Portland whining about the Californians moving north, the people in Seattle whining about the Californians moving north, the people in Tacoma whining about the Seattleites moving south and the Californians moving north, and the people in Eugene/Olympia/Spokane not really being affected...yet.