It needs airlines that are prepared to take a big chance and make a long term committment. Much has been said of the relative cost of flights compared to other airports. The key is that Sheffield is well within easy reach of both MAN and EMA, and whilst the road will reduce journey times between Sheffield and the airport, the number of airlines that would be required to invest in DSA to reduce costs is completely unlikely.
I believe that had DSA opened ten years earlier, it would be a different story now. Just look at LPL, however even at LPL they are losing their grip as the bigger players have wisened due to the change in focus of the short haul market towards low-cost airlines.
Nobody can predict way into the future, one day perhaps there will be a revolution in low-cost long-haul travel from anywhere with a runway long-enough. But then again such routes would still need a large catchment area with high propensity to fly, and the 787 will open up many airports such as LBA which are not as suitable currently for such operations.
People think that because I'm 'negative', I want the airport to close. I dont. I am dissappointed it was built in the first place, but the airport is an employer and I would not wish it upon those employed there to lose their jobs. I just cannot see DSA as a growth area, and as it appears neither do the airlines. If DSA manage to attract any new operators then it will invariably be due to airline disagreements with other airports in the area, rather than the new bit of tarmac.
As far as passenger figures, assuming nothing changes then the losses should bottom out this summer, and possibly improve slightly next year.