That's a good question to ask FIRST, on their championship eligibility website:
http://www.usfirst.org/robotics/2005/cmp_elig.htm
Merit Based Qualifying Teams from the current season -
1. Regional Chairman's Award winners (1 per Regional)
2. Regional Engineering Inspiration Award winners (1 per Regional)
3. Regional Rookie All-Star Award winners (1 per Regional)
4. Regional Champions (three per regional event)
I guess that leaves the fourth out, or maybe FIRST will be kind enough to give the fourth a ticket to Atlanta..