The post-911 airline ticket pricing structure is much different than pre-911. I disagree with pundits who claim that ticket prices at IAD will go 'to the moon.' Just take a look at what's happened to ticket prices for DCA ... they have dropped to the point where I've found some cheaper tickets flying into DCA than IAD, and that's when FLYI was doing 300 flights/day out of IAD.
Just take a look at what happened to (the old) USAirways at PHL and CLT. USAirways had higher ticket prices out of there until Southwest, Airtran, etc went on the offensive and started serving those cities. I don't think that you'll see United jack up ticket prices to the moon at IAD because JetBlue is planning on starting a mini-hub at IAD. One thing that JetBlue has going for it that FLYI did not is rational ticket pricing.
You will see ticket prices that are no longer huge loss leaders for airlines out of IAD. Personally, I think that FLYI did a lot of damage to all airlines desiring to serve IAD due to their fire sale prices. FLYI was giving the product away to the point of pricing tickets well below cost. And that's the reason why FLYI was able to burn through $300 million in less than 18 months.
I'd love it if I could continue to get paid my current wages and find retailers that would sell me everything (from gasoline to groceries to cars and everything in between) for below their cost. Any business that operates on the premise that 'we lose a little on every sale but make up for it in volume' is destined to fail. Anyone who thinks that a business model like the one employed by FLYI will be successful is a lousy businessman.
Bottom line: ticket prices will rise a little bit at IAD so that airlines can turn a small profit. They won't stay at fire sale prices and they won't rise to the point where airlines make a ton of money.