[Sachiel7]

Assuming that this hint is legit,
My guess about the "center being out" has to do with the past 3 years of games. For the three years I've been involved with FIRST, there has always been a large game element in the center of the field. (2002-the goals, 2003-the ramp/bin wall, 2004-the platform/bar)
My guess is that perhaps the robots start in the center of the field, and the game elements are around the outer side of the field. Just a guess...
As far as "Four is not enough", there are lots of guesses. Obviously, the idea that more robots would be on the field is considerable, but not when you realize that FIRST just spent loads of money on making permanent fields for the regionals with the newer dimensions (48x24') and it would be heck to cram more than 4 bots along with field elements into that space. Plus FIRST would have to update the driver stations on all the permanent fields to run 3 hookups (assuming there are 6 bots) to each side. I just think there's too much against that idea.
I'm not sure exactly how it'd apply to the game. My best bet would be that it has to do with either autonomous or scoring.
There you have it.