Your title says a $100k by 2021 yet the content says it will hit $500k, it's contradictory. Well, it's possible but I think we have a long way on that mark and within weeks we are hanging on the purgatory of $9k either we go hell or heaven the next day/s or week/s.
If you are predicting something without any substance you can have any N value and that is what is happening here and it will contradict and once it reach those valuation in the future these predictors will come again pretending that they accurately predicted the valuation in the past. Everyone in the
BTCitcoin space is aware that the market value will go higher with time because of the limited amount of coins and the new investors we will see in the future and it is not a big surprise by any stretch but to evaluate the time period in which we see those valuation is the hard task.