Investors indeed, because Bitcoin's primary utility is as a speculative investment vehicle, the problem is the better it serves this role the worst it becomes as a currency. Bitcoin has developed a Forex market prior to establishing itself as a currency with widespread utility.
I actually think this is the natural and logical progression. First, bitcoin will become a replacement for gold in many people's investment portfolios. As that happens, the price will go up very fast, until eventually everyone who wants some bitcoin has some. Eventually it will level off and people will start using it more as a currency, for commercial transactions.
The reason we're not seeing a huge amount of bitcoin commerce yet is precisely because it's currently functioning more as a highly lucrative investment vehicle. But the era of 10x gains per year, or even 2x gains, is not going to last forever. I'd give it just a few more years.
Then, mass commercial adoption as the last phase of bitcoin's growth.
For more of my thoughts on this, see the thread I started,
The Four Phases of Bitcoin Growth:
https://bitcointalksearch.org/topic/the-four-phases-of-bitcoin-growth-337151