It is easy to see how fast it could happen. If the price leaps up to 1K or 2K a reverse bank run could start, all of the high rollers and investors and people who are just watching Bitcoin would start frantically buying in an attempt to get in before it gets so high that they may never be able to afford a whole bitcoin again in their lives. (or least at a reasonable price)
The last time this happened i think it was regular people all around the world buying, mortgaging their houses and dipping into their savings and such, this time when it happens, all of the high rollers will be involved, the investors buying 5 mill worth of BTC at a time. It could easily get to 10k buy 2015, but that vertical S-curve is what I'm excited about….