It really depends on how many fires are still burning at that time, wind conditions, the amount of rain, etc. The haze has dissipated over much of KL now due to heavy rains, and is only affecting Penang slightly, but all that could change when the downpours end.

If the last haze emergency (in 1997) is of any guidance, the peak haze period would be September. By October, the monsoon winds change and the smoke blows in a different direction. But it does look like there's a concerted effort (and much furor from Malaysia) now to put out the fires in Sumatra before the haze worsens in the next month or so. Cross your fingers and hope for the best.