I sincerely hope they do NOT go with anyone politically affiliated (yes that includes news anchors) for the permanent gig. I have some more thoughts but I don't want to break my own rules here so I'll leave it at that.
I really like Ken for his connection to the show and to Alex but he doesn't really have a narrator's voice. I could see Burton, assuming he does the job capably. I feel like his voice is better suited to the role than Ken's, and he's generally well liked/non-controversial.