Spoiler alert: The answer is very similar to what it was last time. But let’s have some pretty graphs!
As you can see from these graphs, absolutely everything is in a steady downward spiral except 5e. This suggests to me that the recent influx is definitely from more 5e games being started rather than games of other systems being killed, with one exception. Star Wars is in a particularly steep decline, likely due to the Force Awakens slowly fading from public interest. Now that the Orr Group and D&D 5e are officially working together, some amount of 5e’s dominance is going to be due to more prominent advertising.
In other news, if current trends hold I will most definitely need to add Dungeon World to the chart starting next time, because it is currently 0.01 percentage points away from AD&D’s position. Even with the tiny numbers we’re looking at, that’s extremely well within statistical noise. Dungeon World and AD&D are about equally popular.
Source data is here.