In USO he will always be biggest fav with Olderer, they are best HCs in the world. Nadal...just no, and Mugray well, lets see how he will defend it. At RG Nadal cannot constantly win titles till he is 40, and after him Novak has biggest shot.
Novak can't constantly keep making US Open finals only to lose them till he's 40 either.
Maybe next year he'll lose early? Nadal clearly not a favourite at US Open - Murray is up there though - matches well with Novak on fast HC, made 2 finals vs Novak's 4 but better conversion rate of 50%, key issue was mental not the game.
Until Nadal shows decline on clay, which he hasn't yet, he's still the favourite there. And by a significant margin.