Current RNC rule is that taking part in a non-approved debate prohibits the candidate from future approved debates. No major candidate is going to cross that line.
Only 10 can make it to the debate. So suppose the 6 others that don’t make it decide to join Trump in the unofficial GOP debate. It would completely turn tables on who’s in 2nd and 3rd place.
We could see Carly and Carson rising to 2nd place and 3rd place while Rubio sinks to single digits.