There's no more "uncertainty" here than there is as to who won CBS's currently airing Survivor show. The outcome is determined (via secret ballot, etc.) before the series ends but the contestants are just not made aware of it. I'd expect that as with Survivor, the last two contestants only know that they are the last two contestants, but that doesn't mean the winner was not already determined.Mark Burnett knows who won, I'm sure he made Trump make his selection back when the show ended.
There is no way in hell that Mark Burnett is going to edit 16 episodes of this show without knowing the "ending" to his "story," he simply doesn't work that way...
-SB