Unless there is catastrophic nuclear war, like a thousand or more bombs being used, I doubt we will go back to the stone age. However, we could easily end up in the iron age, perhaps something like 16th or 17th century Europe. I have read several books on the aftermath of war with electromagnetic pulse technology. Basically, only a few non-computerized vehicles usable in one case, and in another only horses and no guns, but arrows for defense.
'Survival of the fittest' will prevail despite any of our efforts.