There has been devolopment in the use of a fountain type beverage cart. 16oz of coke from a fountain dispensor costs roughly 10cents compared to 20-30 cents per can of soft drinks.
Steam ovens have been replacing the older convection ovens on newer a/c. This new type of oven minimizes the threat of burning food cooked onboard.
Novelty items such as cappucino makers have come and gone. I'm not sure if there are too many carriers with this type of machine.
Certain carriers to Asia offer a rice steamer.
Other than that the drive seems to be in the quality of food and cost savings by pooling with other carriers in purchasing food products. Example: the formation of e-gatematrix by Gate Gourmet for this reason.