Crabgrass will die completely at the first frost on the fall. It will not return next year from those same plants that grew this year. However, if you (or Mother Nature) provide the right moisture conditions, the seed dropped this year will sprout next spring.

Still you need to get grass seed in in September for your area. Do not wait for spring to seed those huge patches. If you wait then you are guaranteed to have crabgrass next year. There is a tool called a power rake which has vertically rotating cutters. Rent one of those and run over the crabgrass to chop it up. Then rake all that into your compost pile. After you clear the area you can seed. You should have a good idea of how the new seed took by mid October. Then you can decide if you need more seed. But even if the crabgrass returns from watering the new seed, it will die completely this year.

Kill it all now with roundup then get it out of the ground. 9or if you can just pull them all out now) You have time then to reseed this fall. Then in spring use some crabgrass prevention and and kill any weeds and in 1 or 2 seasons youll be fine. Once your new grass grows this fall, fertilize it and again before the first frost and you'll be in good shape.

I had the same problem 6 years ago. Problem went away by year 2. Now none.