First of all, individual boycotts will never, ever overcome a collective action problem, so a fundamentally futile solution is being proposed here.
Plus, this is only bad if Google act destructively evil and no one steps in to change it. If the endgame is control of Chromium being passed from Google to a neutral foundation -- which I suspect it will be -- then everyone wins.
It's always seemed inevitable to me that one browser engine will win out. This is the way of all web technologies. Should we go back to competing variants of (proto-)JavaScript to prevent web monoculture, too?