The timing next year will be different because the marathon crowds will not overlap with the NYE crowds, as they did this year and last, the holiday crowds were absolutely still at WDW when the marathoners arrived due to school breaks, but that won't be the case next year. We have done the marathon every year and always stay from the Wednesday before to the Wednesday after, and crowds are usually fine unless the marathon is early and overlaps with NYE crowds, as it did in 2017 and 2018.