If the GOP effectively kicks him out, boots him from the party (and exhortations from party members to exclude Trump from the debates run along that line), then Trump’s choices are to abandon his run, or to continue but outside of the party that rejected him.
It will be very hard for Reince Priebus and the GOP-e to exclude Trump from the Fox News debate if Trump is #1 in the polls (which he probably is after the past week).
If the so-called leaders of the GOP had a lick of common sense, they would have come down like a ton of bricks on that donor who said they should try to exclude Trump from the debates. That's a good way to move Trump toward a third party run and also to offend all those voters who find significant agreement with him.