If you’ll wait until early Oct to plant (depending on your location) then most of things in the field will likely either be dead or on their way out. Most of it will likely be summer annuals that have gone through their life cycle and seeded out. The exception will be some things like bahiagrass, nutsedge, etc….If you have a lot of issues with those then you’ll likely still want to spray until you get a better handle on them. Help your field progress to better soil conditions over time and it will reduce their presence in your field. You want your summer vegetation to be mostly comprised of broadleafs/legumes with grasses making up a third or less of the total depending on your carbon needs. Its ok to have a small amount of vegetation resprout because by early Oct we’re usually only a few weeks away from the first frost. That will knock out anything that comes back and allow the plot to jump. It might not be as pretty as you'd like for a few weeks but once it frosts you'll never know the difference