JetBlue is going to introduce premium seating on its transcontinental flights between New York and Los Angeles and San Francisco starting early 2014 according to Bloomberg article that you can access here.
The airline has not been able to effectively to compete with airlines that offer first class and/or premium seating on their transcontinental flights.
There is quite a lot premium traffic between these cities. Both United and American have long had planes specifically configured for these city pairs. Good that JetBlue is getting into the game as well.