You are twisting slightly what Trump really said.
What he really said goes something like this...F HE IS REJECTED BY THE GOP in primaries, he feels strong enough about saving the country that he can not rule out run as an Independent.
Note that Trump owes nothing to GOP since he has not received a dime from RNC or any one else.
...and it’s not as if the GOP is doing a damn thing to save the country from Obama and co anyway.