This is a pretty old article (September 2014).
Although the number of bitcoins is finite, it doesn't automatically mean that bitcoin's price will shoot up if adoption increases. You could have bitcoins circulating at a faster rate.
wider adoption means more people spending their coins, but also more people holding their coins in the hope the price increases. and by the time wallstreet pops up and start with buying up plenty of coins the price will shoot up like a rocket.