I would think you should have enough time. Just feed them 1:1 sugar syrup to keep them growing. Obviously the feeding and build-up would depend on the late season/fall flow/weather in your area. You would always have the ability to combine them if they do not build up enough for winter. Of course keep mites controlled so your bees are strong and healthy as they prepare the winter bees in the near future. Overall I think time is still on your side.