From Hell In A Handbasket: Reaching Out

The maximum engagement distance for a handgun is the greatest distance at which you can still get good hits reliably. It might be that a self-defense encounter beyond 50 feet is pretty rare, but I would argue that if you are getting shot at from 60 feet you still have a problem. Rare doesn't mean it doesn't happen, and statistics don't apply to the individual. For many of the victims of Charles Whitman, 100% of their lethal force self-defense situations occurred (and ended) at distances greater than 50 feet.

At greater distances breaking contact and leaving becomes increasingly attractive, unless one cannot leave. If the kids are playing on the playground when incident happens I wouldn't leave them there, I would have to round them up before I could leave. If my marksmanship is up to the task then taking the shot might be the best solution. Depending upon the circumstances you might need to close the distance in order to make your shots (as the Police ended up doing in the case of Whitman.)

It is possible to have a self-defense situation at ranges greater than 50 feet, but the solution will more likely be a function of tactics rather than pure marksmanship. I would not attempt to modify my daily carry handgun to optimize for these sets of circumstances, but I would not focus my training solely on near-distance encounters either.