We can, I believe, make note of some useful facts and determine some likely outcomes. First, let's take a look at why digital advertising got so big so fast. To understand this, we'll have to take a look at some basic economic factors that cause it. Ready?
Search Engine Ads
Search engines have always used ads since the days of Lycos and Alta Vista. They quickly realized that relevant search offered better engagement. Being digital in form, it was also easy to track exact patterns or searches and clicks. The internet was still not quite trusted enough to be seen as credible. In fact, when I was in high school, I was told that internet-related research was not credible and could not be used in essay citations.
Fast forward 10 years to 2005. Google came out with Ajax-search suggestions. It had over a billion users. Advertising became profitable on Google because it solved a useful problem - finding the right business lead at the right time. Web developers began closing a $29 Billion market gap in SEO, of which $4 Billion is still yet-to-be-closed today. (When market gaps closed, they become "industry standard.)"
In the next 5 years at this rate, SEO and mobile responsiveness will be considered industry standard and will no-longer be a competitive edge to sell.
Let's look at some numbers I found from Statistica (these are rough for sake of ease):
The newspaper industry lost 45% of its market share between 2001 and 2008. When the financial housing bubble burst and big banks failed, the Fed responded by pumping $4 Trillion into the economy from thin air. The result was massive job loss and lots of inflation.
One way companies in cahoots with the government (like Google) mask inflation is to replace bubbles with their solutions. At the same time 45% of newspaper market share was lost, 30% of that was taken by Google. This means that ~15% of the money supply was no-longer in the economy, and was "freed up" in order to buy bank-funded treasury bonds.
What Does This Mean For The Future?
As far as internet marketing goes, we can count on mobile transactions to replace paper money and re-shape the internet. One reason for this is in order to keep the financial institutions limping along, they will eventually need another bubble. The next bubble is anybody's guess. But it's possible that all computing will be done by phone and tablet instead of desktops and laptops within 5 years.
Therefore, digital advertising will be even more content-based, and in-mobile ads will likely dominate the advertising sector, alongside search ads. One reason for the collapse of desktops and laptops is simply because they require more raw materials to produce. Plastics are often derived from oil, and circuits from gold and silver. Now that phones and tablets have similar computing power but with less material use, we will for this reason likely see a collapse of the desktop computer market, thus shifting all digital ads to become mobile-centric.
I could go on but I'm sick and sleepy.