There were several studies over the years about the money made from apps. The distribution is very exponential. IIRC, something along the lines of 3% making some 80% of the money. Moving up a few percentage points can make a huge difference.
In addition, one study showed that 65% of the users downloaded zero apps in a month. The stats went to 74% just to get to 1~2 apps/month.
App discovery is a huge issue and can be very costly. One case was a timer app that was touted as awesome, yet it failed to get noticed.
The increase in sales in the appstore isn't going to help most developers, until and unless the distribution changes, most apps will continue to struggle just to break even. Most apps don't break even.
As apps continue to get more complex, the skills needed to develop a great apps that stands a chance, the cost and time investment will increase.
This won't change direction, in fact, it'll get harder and harder to develop a high quality app as people will expect more.
What can change, and probably will, is at some point, the lower end apps will just fall out of the system and die off. At the same time, lesser skilled developers will fall out of the system, and just like any other platform, those with the best skills will remain.
Clearly the appstore has changed, it's been undergoing this change for a while now. Devs have been talking about the gold rush being over for a few years now, just like any new bubble, the weak die off. Some of the strong will die off too, but it'll all pan out sooner or later and become a normal market.