This prediction is extremely pessimistic. Bottom to happen only in October 2019. One month until then? It is still possible but i believe bottom will happen way earlier.
Those predictions seem to be based on a mathematical model, and as any model it can fail. McAffee also used a mathematical model, as many others, but at most only one model is going to be true.
McAfee used his penis as a "model" to come up with a prediction. that is why he wanted to bite it on TV if it didn't come true.

but in all seriousness, the whole prediction thing when it comes to speculating the price of anything is based on something that is never 100% reliable. that is why people call Technical Analysis a pseudo-science.