I know this is a rhetorical question. For most of us though, we'll never be able to plan our last flight.
If the government was to shut the airspace down permanently, the circumstances around it would probably outweigh the desire to go on a pleasure flight. Also, the circumstances would probably cause an immediate shutdown...like on 9/11.
Those of us who were pilots back during 9/11 remember that feeling of wondering if our last flight was...in fact, our last flight. Some of us in the Washington D.C. area wondered if our airspace would shut down to GA permanently.
Considering the circumstances associated, my last flight would probably be loading up my wife, kid, and dog, and bugging out to Canada.