I could echo a lot of what has already been said. The core dynamic seems to be the likelihood of a tedious "Novandy" (good one) war of attrition throughout the whole year, and whether or not Rafa and Roger have anything left to challenge them. There are some interesting challengers: Stanzilla is clearly still dangerous (although at some point will collapse quickly, imo, maybe even next year), and hopefully del Potro can continue his comeback. Milos seems to be pulling away from Kei and the rest of his generation as the main threat, and Cilic has occasional bursts but doesn't seem to be able to sustain it.
Thiem heads the next pack, with a new group of challengers and future 2nd tier players. Kyrgios will likely fit the Stan/Cilic/Safin mold of very dangerous when focused, but erratic. Pouille is an interesting player that should be with these two as future top 10 players, but not the leaders of the pack.
I'll also be watching Edmund and Khachanov to see if they can "do a Pouille" who "did a Thiem" this year. I could see Daniil Medvedev being the next in this line.
And then we have Alexander Zverev, who is the current best hope for a future elite. I think a good year would be him getting to the cusp of the top 10, but I'm not sure he's going to break in until 2018. 2017 will be about winning some more minor titles and going deeper in Slams, maybe even challenging for a Masters. The rest of the young guns are a ways from being relevant. We have to see if Fritz can take a step forward as he's stagnated since the spring. Players like Tiafoe, Kozlov, Lee, and Rublev will be fighting to get into and stay in the top 100. I'm ready to write Coric off as nothing more than another Bernard Tomic/Andreas Seppi type. He'll probably sneak into the top 20 at some point, but will mainly hang out in the 20-50 range.
On the way out: Gasquet, Berdych, Tsonga, Ferrer. Maybe Tsonga and Berd hang around the 10-20 range for a couple more years, but I think they're getting pushed out of the top 10 for good. I think Monfils will slip back rather quickly.
Random players I'll be watching: I could see Pablo Carreno Busta making some noise during clay season, maybe winning a title or three, even an ATP 500. Also, like some I could still see Grigor Dimitrov doing something...what, I don't know, but I could see a surprise Masters title and/or a Slam final appearance...probably not a Slam title, though.
Finally, as boring as a Novandy tandem could be, what makes 2017 interesting is that after those two the top ten is entirely up for grabs. Sure, we know the basic players who have a chance of being there, but the list is pretty long and it is unclear who will make it, and in what order, and there are several dark horse candidates.
lot
