Sushka, no JetBlue has not received their A320 orders yet and is exectuing their 20 flights daily schedule with a fleet of Fairchild Metroliners and a leased prototype A380 from GATX.
TheCroupier, I disagress with your estimate. It is the opinion of this poster that JetBlue's sucess to OAK and ONT clearly shows that there is a demand for low-cost transcon flights from JFK. Also, JetBlue's profit margin is much higher on long flights than on short hops, plane burns fuel less and overhead is spread out over a longer time. Also, you made the point of aircraft utilization, well the first OAK and ONT flights were red-eyes operated all night when the planes would otherwise be asleep at JFK or one of the east coast stations. I would assume that any new west coast service (such as SEA and DEN) would also be these red-eyes, just as OAK, ONT, and SLC are now. You may have read that JetBlue is adding a 2x daily to OAK and ONT, this means that yes one aircraft will have to be devoted to each route to fly both R/Ts, but the DEN, SLC, and SEA flights can be flown with already owned aircraft that will come back to New York around 6 or 7 pm from their daily rotation, fill up, fly 5 hours to the west, drop pax off around 9 or 10, fill up again, fly back east, and drop pax off around 6 or 7am, and be cleaned in order to again fly the daily rotation up and down the eastern seaboard.
PS: Just checked fares at JetBlue.com, these transcons are not cheap, last minute flights are 500 bucks and ones 2 months in advance are around 300. Not bad.