The chart is sus. In the absence of good news it should be gradually decreasing, not gradually increasing.

TF2 community has a joke, that Valve lost the war against bots and it is easier to make TF3.

Talking about "decreasing". This does not apply by default to all things.

Let's say we have a student, which has a deadline. The probability stays constant, even if he has not started yet, because productivity increases in the last hours.

There might be is a hidden deadline for Valve.