I just watched the Doha 200m on YouTube; Ameer Webb looked amazing. Webb ran 19.85 in a DL meet with an almost perfect +1.9 wind. I almost forgot Merritt ran 19.78 in mid-April with a +0.9 wind, with the closet competitor about a half second away. Right now, there are 4 solid sub-44 400m sprinters, Van Niekerk, Kirani James and Isaac Makwala. All three of these guys are almost a decade younger than Merritt and are at the top of their game. I am not saying Merritt can't win the gold in Rio, but getting past Niekerk and James is going to take the race of his life.
On the other hand, Merritt's is the best 200m sprinter in the world right now. I know Bolt and Gatlin haven't run any 200s yet, but I don't think they could have run faster than 19.78 in mid-April.
Should Merritt consider running the 200m or perhaps doubling in Rio?