I definitely agree with you. In a nutshell, Bitcoin's exponential growth is a result of hype. This isn't necessarily a bad thing - Facebook's initial user growth was also exponential, and that eventually stabilized. The question is, what happens when the hype behind Bitcoin dies.

I believe that, like you mentioned, it depends on Bitcoin's utilitarian value as a currency. If it turns out Bitcoin is more useful than, say, Paypal for facilitating actual transactions (as opposed to being a pure investment vehicle like it's being used now), then its price should encounter steady growth. If not, then things will get interesting.