Being fast in a particular sector is one thing. Actually making that advantage count and sticking an overtaking manoeuvre is a completely different story.
Hamilton is the best overtaker in F1 right now, so maybe he could manage this on Vettel, but I highly doubt it. Button is definitely not a good overtaker, so to expect him to overtake a faster car (driven by the Worlds best driver), in sector2, after the race has started, is taking a big leap of faith. Especially when you consider that McLaren and Ferrari seem to have a car which is similar in performance, on this track.
I know that there are many Button/Hamilton supporters in here, but some people need to get realistic.
My belief is that the only overtaking action, among the front runners, we shall see tomorrow, shall be off the line (and maybe during the pit-stops). With the 2 McLarens starting on the dirty side of the track, their job will be very difficult.
Once the race starts, expect to see a procession, a la Bahrain.