Your question assumes that I MUST bet on one person.
I wouldn't bet on anybody at this particular moment, including Bolt. All the top guys have a good shot. You must also consider that a year is a long time to the young guys, and leaves room for plenty of improvement in guys like Blake, Lemaitre, Ashmeade, Makusha, Salaam, Mitchell, and even maybe Demps. And one cannot forget about the possibility that Rodgers and/or Mullings will return!
If a gun was to my head, I would pick Blake in both the 100 and 200.
Blake is a disciplined runner. If somebody is even with, or ahead of, Bolt at 75m, Bolt grips. Blake on the other hand lets speed flow, like Gay used to. Now that Bolt doesn't exhibit his amazing starts of yesteryear, he will not be in front at the halfway point.
Blake, Powell, Carter, maybe Thompson, Mullings, Rodgers, etc. will be in front of him. He will be with Lemaitre, Salaam, Makusha, and will need to relax to win.
Blake, on the other hand, is so jacked that he's totally inside his own head, just seeing what heights he can scale. His 19.26 opened even his own eyes to his greatness--it's like he's running in a trance.
All Blake needs is a start, and he will be untouchable in the 100 this year, unless Gay is healthy and has a start (unlikely), or Powell actually performs (also unlikely).
The 200 is a different story. I was not at all shocked by Blake's 19.26 performance or Dix's performance, but I was shocked at how well Lemaitre closed in the last 50 at WC's, and how tightly Bolt was gripping in the last 50 at WC's.
The battle for gold will be between Blake and Bolt. The battle for bronze will be between Dix, Gay, and I think Lemaitre if he gets better intermediate acceleration in the curve. Lemaitre is so robotic that the slightest thing can throw him off--like a curve. He absolutely needs an outside lane to perform well...on the inside, I think he will get crushed.
If I had to pick right now, it would be Blake. His 19.26 was easy and controlled, while Bolt's 19.40 was difficult and tight. All Blake needs is to have Bolt beside him instead of Dix to perform better--and all Bolt needs is Blake beside him instead of Dix to perform worse. Being beside each other would be the best situation for Blake, and the worst for Bolt--and it could very well happen that they will be side-by-side in the final.
So much depends on lane draw also. Here's the thing--in the 200, if you are outside somebody who you know will be a serious threat, you really have to know how to run from the front, to be your own reference rather than reading off somebody else. Bolt can do this very well--can Blake? I think so, he seems to be inside himself...but then again, he didn't shift into top gear until Dix pulled alongside him. Dix he can blow away, but Bolt?
Yes. Bolt will tighten up. Blake is jacked. He could run 250m at the same speed, the way he's running.
Gun to my head? Blake in the 200.
But I wouldn't bet on anybody right now.
Look, Johnson seems like a genuinely nice guy. I'm surprised he didn't come out of retirement the moment Blake (who?) beat his 19.32 while missing the start and having a WR run.
After all, if Blake (who?) can miss the start and run 19.26, MJ should surely be able to go 19.1x, right?