What kind of databases are trending? (becoming popular more)
As you can see, there is an increasing popularity towards non relational database systems. I was surprised to see the graph DBMS curve. But then again, the rise of sensors and connected devices, which produce so much graph data, should be no surprise to see the above trend.
In the chart above, it may give you the wrong impression that organizations are moving away from relational RDBMSes. However, that is not the case. All DBMSes except RDBMS together makes only a small market (around 10%). Therefore, small change in popularity for non relational DBMS is very visible. To confirm this fact, look at the chart below. Still RDBMS rules the world! IMHO, it will remain this way for the foreseeable future.
What kind of databases are people building these days? As you can see, most software companies invest on relational systems. However, at the same time, they are investing more on other types of database systems mainly due to the following facts:
1. Amount of data is getting bigger and bigger (e.g. "every two days we create as much data as up to 2003", Google CEO)
2. Data is more connected than ever before (e.g.: rise of social media, sensor networks, connected devices; Cisco estimates 50 billion connected devices by 2020.)
3. Data is unstructured or semi-structured (e.g.: Amazon review comments, tweets, blogs)
I encourage you to visit db-engines.com to see more drilled down stats.