Demand for USD is drying up. I don't see this as a bullish signal for equity markets, perhaps a very brief bullish reaction if so. I see this as a massive straw preparing to break the camels back. Demand slump is involuntary. A window into the state of economies outside the U.S. Seasons change. Welcome to Autumn.
In the case of a pop, I see $4300 being the ceiling for the S&P.