I think it's got less to do wtih Eisner than with the dollar vs. the Euro. The general consensus is that the best (or only) shipyards with the capacity to build a third ship are going to be in Europe (Italy, mostly, maybe Portugal). The problem right now is that the dollar is very very weak against the Euro. And even with the bajillions that Disney makes, they know they have the ability to hold off for a little while and let things even out.
If there's no third ship, the demand stays high, and so can prices. There was a big report about a month ago about how the price of cruising has gone up 40% in a decade. But to my knowledge, the Disney ships sail at or very near capacity three times a week. So crazies like us keept the demand high.
Plus, with no third ship, they can do the special cruises (repo out and back, plus the west coast trips this summer). Those not only generate huge revenues, but also a lot of industry buzz and publicity. My guess is that if there is overwhelming demand for a permanent west coast ship, and their marketing predictions say they can both fill it weekly and keep the original two filled out of Florida, then maybe Disney will be more apt to suck it up and take the initial hit on the construction capital for the third ship.
If not, well, I dunno. Forecasts are mixed on which way the dollar is moving against the Euro. The stronger the dollar gets, then certainly the closer Disney will be to pulling the trigger.
It's my understanding that the plans for the as-yet unnamed third ship are mostly complete, so now it's just (as always) a question of money.