I don't think that Pan Am is going anywhere.. For the aforementioned reasons, as well as the fact that the market up here in Southern NH, Southern Maine, and even Northern Mass. can, and has supported a number of competing airliners.
If I recall, US Airways operates a couple of commuting flights into IAD (or BWI), so there is some competition on that front, for both Pan Am and Atlantic Coast. While Manchester is convieneint, and pretty easy to connect to hub cities from, PSM is just as easy for Pan Am's niche market (as stated, primarily Florida) travelers. We won't even talk about that hellhole called Logan. If I want to go to Florida, I have a number of choices in New England, as far as budget airlines go (AirTran, etc).
The population density of this area is very high, leading me to believe that there is certainly room for a number of competing companies. Of course, if Pan Am could initiate flights into some larger hub cities (ie CLT, PHL, or even ATL) and survive the landing fees, they would be a far more viable competitor.