Move to diesel engines across the RV spectrum a fad?

IMHO they are always looking for a way to change the rules of the game. Don't get me wrong I love Diesels. However, the upkeep is much higher, fuel is higher,it will require a lot of certification of mechanics to work on them, (that is going to increase the price of service). While longegivity is better, the fuel mileage has come way down on the bigger diesels. Fuel prices will probably rise substantially as diesel fuel competes with heating oil for market.