I agree that Prestwick is looking a bit shabby these days as a result of under investment over the years. It is not difficult to see why many have such a pessimistic view of the airport's future. However, I believe there are a few points that might be worth remembering.
Ryanair may well have reduced the number of services that they operate out of Prestwick but have I believe their largest maintenance, overhaul and refit facility there. I think they have about 400 staff working there. Surely, its in there interest that it remains open or they will have to relocate the work, which would be expensive.
I understood GLA do not want Ryanair there as they do not pay enough. O'Leary needs Prestwick just as much as Prestwick needs Ryanair. The airline only has the upper hand in the deal due to its size and negotiating power. They will secretly be delighted the price of the airport has come down. That means they can bully its new owner into allowing them to use the airport for next to nothing. Then the number of flights will begin to increase again.
In recent times the number of routes operated out of EDI by Ryanair have been cut. O'Leary im sure has complained about the high cost. As demand for air travel grows it will be harder for Ryanair to get the cheap deals they depend on.
BA have also leased a hangar for the next five years.
Although Virgin decided against using the airport recently the fact that they considered it shows Prestwick must have the potential.
Infratil have failed Prestwick. I really hope a new owner is found soon. One that is willing to invest in it.