Are you getting these "stages" from somewhere reasonably official, like an economist or something, or are you making them up? 'Cause I'm not an economist either, but I don't think stages are best concept to approach currency adoption with.
The only thing that really matters when increasing the spread of bitcoins is increasing the things you can get for them. When you can buy something tangible with bitcoins in an easier manner than any other means, bitcoins, for you, have value.
Currency exchanges are a important and useful element, as they tie bitcoins into other measures of worth. Everyone likes money. That'll only get you so far though, because other than laundering money, there's no reason to exchange cash for bitcoins for cash. A market where everyone's an investor can't be much more than a hobby. Seeing as this is what 80% of the Marketplace chatter is about (with another 15% being casinos), I feel this niche is pretty well saturated.
However, services which only accept bitcoins are where value really comes from. It expands the economy coming and going: the people who use them need to have gotten bitcoins somehow, and people who receive the bitcoins need to spend them somehow. This kind of service could be standard internet sites which consciously choose to only accept bitcoins (as my site does), or it could be the only real option for certain commerce markets (like Freenet), owing to bitcoins' security and anonymity.
In any case, before this turns into a real ramble, I don't see any "stages" anywhere. Just continual growth, or lack thereof, in small or large amounts, with a critical mass somewhere in the hopeful future.
No, no, no. We're just trying to describe and predict the growth of the bitcoin economy.