In one embodiment, a method comprises: determining, by a network device in a wireless data network, a past throughput of broadcast data packets transmitted at broadcast transmission intervals of a prescribed broadcast schedule over a selected measurement interval, the broadcast transmission intervals each adjacent to unicast transmission intervals allocated in the wireless data network, each of the broadcast transmission intervals in the prescribed broadcast schedule initially set at a prescribed duration; predicting, by the network device, a predicted throughput of a future broadcast transmission interval of the prescribed broadcast schedule, for transmission of at least a future broadcast data packet, based on executing a trendline prediction of the predicted throughput using the past throughput over the selected measurement interval; and adjusting the corresponding prescribed duration of the future broadcast transmission interval, relative to the corresponding adjacent unicast transmission interval following the future broadcast transmission interval, based on the predicted throughput.