Not really. The schedule is normally based on the average gate to gate time with an element built in to allow for delays at either end. This has the dual advantage of both a built in schedule buffer, and minimizes the number of occaissions that a flight is seen to be arriving late.
Flights are generally filed at a constant mach number. Straight in arrivals and direct routings will obviously shave a few minutes off the planned flight time here and there.
Bear in mind that most delays occur either on the ground, or during holding/spacing vectors prior to landing, and the schedule is constructed to acccomodate a significant element of that.