So, confirmed participants in GOP debates will be, as of today:
Romney
Giuliani
McCain
Brownback
Hunter
Paul
Tancredo
I don't think Huckabee has formed his committee. Have I missed anyone?
He has the same chance as Hunter, zero.
Your list is correct, thus far.
I think Tommy Thompson formed a committee. I'm not totally sure.
Someone mentioned Gilmore.
Updated list of who would be in GOP debates, assuming all of those who have formed ec's will last until debate season (most assuredly they will not all last):
Romney
Giuliani
McCain
Brownback
Hunter
Paul
Tancredo
Gilmore
Thompson