The thing you're leaving out, is that the current market cap is largely based on demand for interest earning coins. A demand that has to level out eventually and can quickly reverse if 1000 dash stored in master nodes suddenly become a losing proposition
Apparently not. (According to 2.5 year's worth of trading and nodecount correlations

).
2.5 years of steady increase in # of masternodes will do nothing to help you predict what happens when that node count levels off, and eventually goes down, flooding the exchanges with its contents.