Given the current situation, hedging is also not a realistic option for the other airlines; as your post makes clear, even WN's hedging is decreasing as time goes on:

From http://www.house.gov/transportation/.../release5.html:

Even the most successful low cost carriers are likely to run into difficulties on the hedging front in the short-term. With oil prices so high for so long, no investment bank is willing to cover $26 barrels of oil for anyone, no matter how much cash the airlines can put up front. As a result, only Southwest will have fuel hedges in place in 2009, but just 30 percent of its total fuel requirements at $39 per barrel.

Consequently, hedging is not going to insulate the airline industry from higher fuel costs beyond the next few years. By the end of the decade, all airlines will have to face the reality that their core business can be the only guarantor of success.