Not gonna be released during Diwali, if we get it for New Year, that itself is soon enough, i would fairly target it for Next Year Build conference in April
Looking the way Nokia/Ms have released the WP 8.1 it Should be released before Mid Oct.
Lumia 630 and 530 were released very soon after their launch, so hoping to see that trend.
MS/Nokia knows India is one of the biggest market for WPs.