The Slippery Slope Million Dollar Logistic Model, is based on the fallacy of what occured in the past must continue in the future.
To a certain extent, the past bitcoin price series does suggest a prediction for the future. Namely that there were bubbles and there will be more bubbles.
You misunderstand the mathematical nature of the logistic model when you state that it assumes that what occurred in the past must continue in the future. Eventually, the exponential growth of bitcoin prices must end. The logistic model is the simplest way to explain that phenomenon - that eventually future bitcoin prices will not have the exponential growth observed in the past, as we pass the 50% adoption rate by the population of possible bitcoin speculators. For a maximum bitcoin price of 1 million USD, the model predicts the halfway adoption point at year end 2016.