0.17 is a decent reaction time for Bolt. He hardly ever reacts faster than that. At the moment, Gay would probably be ahead of Bolt at 70 or 80m, and Bolt isn’t used to that. I’m not saying that Gay will beat him, but he should certainly be able to push Bolt all the way to the line.
Bolt’s start has been quite bad this season, probably as a result of the long to short approach he seems to have followed. His top speed and SE is certainly in place, and if he can get his first 30m back to where it was last year, the world record should definitely fall.