There's no need for any doom and gloom over the prospects for DSA. It's had a great start, despite opening too late to capitalise on the revival in air travel post 9/11, at a time of (temporary) economic decline and in particular very high fuel prices.
There may well now be a short period of consolidation, but I expect steady growth over the next few years overall. You can't take away the fact that it is situated close to the East Coast Main Line (unlike any other airport except arguably Newcastle) and is at the Centre of the motorway network.
LBA is even difficult to get to from the Centre of Leeds (I know I've done it in the middle of the day), and MAN is a pig to get to from anywhere East of the Pennines. Even EMA is subject to the frequent problems on the M1.
Surface travel in the UK is becoming so difficult these days people are keener than ever to have a decent airport on their doorstep. That's what the several million people in Yorks, Notts and Lincs want from DSA, not necessarily another MAN but if we have plenty of choice for holiday flights plus links into a hub like LHR for long haul we'll all be happy.