Frank Castle is dead and there really is no other way to end this story. What made this series so great was that Jason Aaron took the character seriously throughout the whole run, and by making the Punisher a real-time Vietnam Veteran (he's in his mid-sixties) made a psychotic killing machine into someone you root for even if you don't really want to. Although touching on other Marvel villains like Bullseye and Kingpin, Aaron keeps you interested the whole time because there is a possibility that Frank could just drop dead at anytime.