The price is surprisingly easy to predict based on the previous rallies.
However there might indeed be a blackswan event that will drive the BTC to 700 000 USD at this rally. The probability for this is perhaps 5 % or less.
I'd like to see coinbase keep up with that demand.
"Due to volume, we are unable to fulfill instant buy orders. However, you may purchase now and your order will be fulfilled in six months. Thank you for your understanding."