It looks like Valve has either started work on something or is in the process of finalizing it.
The increased number of Valve developers on test servers almost always means something, most often some major news for CS: GO. Of course, we shouldn’t get too excited, because we don’t know what it is yet.
However, in fact, the last time so many people tested something else was in April 2021, i.e. in the first half of the year. Since then, there have been a maximum of 2-3 people on the test servers.
Increased number of Valve employees
This amazing amount of people testing something is exactly 4 developers. It sounds funny, especially with such a huge production as CS: GO, but it is 4-5 people who always test new operations, for example.
We could debate that it is definitely about an operation or at least some winter mini-event, but in the case of CS: GO, nothing is certain. This is more of a hint that Valve hasn’t forgotten about CS.
In the past, 4 people on test servers did actually mean that an operation is on the way, but it might as well be some kind of bug, a glitch that the developers want to work on. So it has to be approached with a distance.