Killing Floor is impossible. Even with ARG people helping. The playercount when the progressbar was at 0% (yes, I was there), was around 20 thousand. That's not including ARG players, they were probably people playing games for fun.
Now if you look at all the people involved in the ARG, in this case, taking the member-count of the NELIPOT Steam group, which is now, 54,000 members, with 34,000 members online (16,000 ingame). With the current activity of the ARG and people playing the Potato games as of this moment (25,000), we can safely say that around 5,000-10,000 people, give or take a few thousand, have worked on completing GLaDOS's reboot.
So when all the games except Killing Floor is done, we'll have around 16,000 people working on Killing Floor's bar. This doesn't even account for people who don't own Killing Floor (me included), so for the benefit of the doubt, only 10% will be docked. 14,000 players focusing on Killing Floor, compared to the 6,000 now, when the other games in the ARG are not yet complete.
Currently, the ETA for Killing Floor is 7 days to completion. With a little more than double the current rate of Killing Floor, we'll be able to cut down the ETA of Killing Floor to a little more than 3 days. That's somewhere on Tuesday afternoon.
I'm throwing the idea on the table that this is a huge marketing ploy that won't get us Portal 2 early. A few hours at most.