The may be possible or may not be. No one knows for sure. To reach that price point, the bitcoin market cap should be somewhere to close 7.5k billion USD. The current market cap of bitcoin is 110 billion USD. So the current market cap needs to be 7500 billion USD for the bitcoin price to reach $500k mark. I believe, that is not going to happen in three years. This exponential growth will need support from organized financial market as well as form the governments. If we see some economically strong countries legalizing bitcoin, then it can be possible but otherwise not.

I have found a very interesting tool to calculate bitcoin's price based on its market cap. Try it for yourself to know the prediction.

http://worldbitcoinnetwork.com/BitcoinPriceModel-Alpha.html