Sorry but I think John Mcafee is nuts, bitcoin will not hit one million dollars within the time frame he predicted. Johnny just craves attention, that is why he makes all these crazy predictions.
Even just reaching 100k is unimaginable.
Bitcoin price is unpredictable, so we can not make amy conclusion yet. Actually there are some analisys methods that we can use to predict bitcoin price at certain time. John Mcafee is an expert so maybe he make that statement based on his analisys. But its not mean that it will really happen. I don't have any doubt about bitcoin reach $1.000.000, there are many posibility about it.