You can find the official information here:
http://www.usfirst.org/robotics/res_art9.htm
From what you've said, your team doesn't qualify as three top rookie seeds gives you only 3 points. You need five to qualify. However, last year there were slots left open because teams who were already qualified won "reserved slots" like those for Regional winners. Those slots were made available to all teams just before Nationals. No guarantees this will happen though.
Keep waiting and watching and fund raising. Better yet, win your events.