OK so this is a really hard call.
Weir's a 19.8 guy but has been inconsistent.
The guys who have been racing 200's this year look like this in the world rankings, in order of performance not accounting for wind:
Edward - 2,6,8,10,22,31, with a worst time of 20.23(-1.5) (1st in a smaller meet)
Ashmeade - 3,9,13, with a worst time of 20.13(-0.2) (1st over Weir in a big meet)
Weir - 1,20,47,48, with a worst time of 20.31(-0.2) (2nd to Ashmeade in a big meet)
Lemaitre - 12,33,45, with a worst time of 20.30(+1.3) (1st in a small meet)
Mitchell - 14,26,44, with a worst time of 20.30(+1.3) (5th in a big meet)
Dwyer - 7,30, with a worst time of 20.22(-0.1) (1st in a semi)
Gatlin - raced once for a win, means nothing
Gay - hasn't raced yet
Ashmeade > Mitchell. His worst time is better than Mitchell's best, and his worst was a win over the excellent Weir
Ashmeade > Weir. IF Weir's 19.8 #1 is thrown out, Ashmeade > Weir, for the same reasons stated for Mitchell, but even more so because Ashmeade has beaten Weir head-to-head; BUT Weir beat Ashmeade head-to-head, so this comes down to consistency; by that measure Ashmeade > Weir on the season
Weir > Mitchell. Better best result, better worst result considering wind, better placements in big meets.
So for the 3 of them, I have Ashmeade>Weir>Mitchell
Lemaitre > Mitchell. Roughly same overall placements. Same worst result, except Lemaitre's came in mid-May, whereas Mitchell's came at the very end of June. Lemaitre has shown noticeable improvement on the season, and will be running close to home.
Weir > Lemaitre. Not by much. Better placements in big meets notwithstanding unimpressive overall performances. #1 performance needs to be considered, Weir has shown a flash of brilliance that Lemaitre has not.
So for the 4 of them, I have Ashmeade>Weir>Lemaitre>Mitchell
Edward >= Ashmeade. Not by much. His worst performance was pretty much equal to Ashmeade's, both of them having done only what they needed to do to win. He has won every 200 this year except for NYC where he lost barely to Ashmeade, and significantly to Weir. 2.5 weeks later he improved his best time to essentially equal what Ashmeade had done in NYC, beating Ashmeade in the process. Head-to-head they are equal, but Edward has the favorable trajectory, but only by the smallest margin.
So for the 5 of them, I have Edward>=Ashmeade>Weir>Lemaitre>Mitchell
Dwyer > Lemaitre. Dwyer has run only 1 meet, but it was at the very end of June, and was a pressurized meet in Jamaica that he won, both in the semi and in the final, beating Weir in the process. His 2 performances this year are better by a little bit than are Lemaitre's 3. They are just about even, but Dwyer has beaten Weir, whereas Lemaitre has lost to Edward and Ashmeade.
Dwyer >= Weir. Performance records are essentially equal, maybe an edge to Weir because of the #1. Trajectory favors Dwyer, who beat Weir head-to-head at the end of June.
So for the 6 of them, I have Edward>=Ashmeade>Dwyer>=Weir>Lemaitre>Mitchell
Now the wildcards, Gay and Gatlin.
Gay >= Edward. Gay has recorded a much better 100m, although he looked like he was laboring compared to Gatlin who beat him in that race. He was matching SE with Rodgers who has been very good this year. This is a huge unknown, but assuming that Gay is progressing in his training, he is better than Edward, though not by much.
So for the 7 of them, I have Gay>=Edward>=Ashmeade>Dwyer>=Weir>Lemaitre>Mitchell
That's as far as I will go with the bs. The >= measures, you can switch the order. Mitchell will lose, and Weir/Dwyer will beat Lemaitre, who will beat Mitchell. Also, Gay, Edward, and Ashmeade will beat Dwyer, Weir, Lemaitre, and Mitchell.
The only remaining question is Gatlin. Based on how he destroyed Gay in the 100m, and how Gay wasn't gaining on him at the end, and how Gay seemed to be laboring a bit at the end of his second 100, and the fact that Gatlin is in 9.80-flat 100m shape (incredible), it is hard to bet against him. Not only has his start been excellent, his top speed maintenance has been good as well, he looks to have better recovery this year than in years past.