Exponential curve fit to Bitcoin

The price graph of Bitcoin looks a lot like an exponential curve, so I got some historical data from CoinMarketCap.com, then used Xuru's Regresson Tools to fit an exponential curve to a sample of data from the past 200 days. Here is the equation:

price = 1787 + 463 * exp(0.013 * day), where day 0 is May 10, 2017

Here is a graph showing how good the fit is, from Meta-Calculator.com:

By day 400 (May 14, 2018), a bitcoin should cost $85,716. Bitcoin would have a market cap of roughly $1.5 trillion, which is comparable to the GDP of Canada, the 10th biggest economy in the world. But whereas $1.5 trillion is the productive output of 35 million Canadians for a year, what is Bitcoin producing?

Bitcoin is not producing anything, rather, by then, it will be consuming about 300 billion kWh per year of electricity (multiplying the current annual consumption by 10). That would be about the same as Great Britain, the 11th biggest electricity consuming country.

So, people buying Bitcoin at that level would be buying enough electricity to run Great Britain, except that it won't be running anything, just generating heat. In return they would get shiny bitcoins. Wait, bitcoins don't shine because they aren't tangible.

What could go wrong?