I mean, best case scenario, the things we've all concluded a long time ago will be reconfirmed even more clearly - that Clinton would make an uninspiring, flawed but 'safe' president, while Trump can't be trusted with enough responsibility to run a grocery store, never mind the presidency of the United States. And people will still not care about either of those facts any more than they did before.
Worst case scenario, it turns out that Trump has in fact listened to more than just one out of every ten words Conway said to him, and is even willing to go with her advice for a bit, in which case he will look like he might conceivably be able to handle said grocery store, and hence he should get the nuclear codes. Clearly.
Don't think either outcome will sway too many supporters of the other candidate, but then that's not what it's about - it's about the third party or undecided voters, small as those groups are. And that handful of moderate Republicans looking for any flimsy excuse that Trump can give them to set aside their revulsion long enough to cast their vote for him.