Rickard's prediction assumes past performance is predictive of future returns. Maybe, maybe not. One thing that is niggling the back of my brain though is that the money supply growth during the periods Rickards cites was on a much flatter slope than what is occuring right now. *If* his thesis is correct, and *if* the bull market is related to moentary policy (ie. growth of Fed balance sheet / money supply), this bull run might see more growth than he's expecting. Of course, the US and/or global economy could devolve into a destructive deflationary spiral and everything could go in the toilet.
Schiff's comment doesn't address the fact that US Equities are in a Fed created bubble and have absolutely no basis in reality anymore. I'm not sure that's really the key variable you want to use in an equation for forecasting anything.