The only growth your seeing in the BTC economy is the growth in demand to speculate.  Actual goods and services transacted in BTC are flat or barely rising, and even that is mostly commerce that would otherwise have occurred in USD even without BTC existing.

My suspicion is that miners are hoarding most coins right now because they can cover their energy costs selling just a few.  We will see difficulty increase until it becomes self limiting and once all miners are forced to liquidate to pay for electric costs the price will crash as their is no way that people will put a half million dollars a day into buying newly minted BTC, the amount necessary to sustain the current price.