OP's disclaimer: I started this hobby project one year ago. The point of this project was and still is to learn about new technologies. Maybe I am lacking the statistical background, or the data since it goes back only 13 months, to make such an statement but when I starting seeing these trends in the number of job posts, I thought that it would be interested to share it in the Hacker News community and get some feedback.
About whether these trends that we see in the graphs are something real or just a data issue like seasonality or a problem with the data sources, I think we will soon know from the mainstream media. As always the time will tell.