No way. Chickens are extremely good at adapting, and most handle going wild just fine. There are several areas where chickens have gone feral and they flourish. Check out Fair Oaks, California. They have so many feral chickens that they celebrate the audacious bird. The precursor to the chicken, the Jungle Fowl, still roam wild in some areas as well. Yes, some breeds won't do as well. Breeds that have been heavily altered by humans into laying more eggs than normal or growing heavier far quicker than normal will probably die off. Especially meat chickens, as they are very lazy and don't do much besides eat and have heart attacks. But the bantam and game varieties of chooks will probably do just fine.