Google is your friend. Propane is not going away as a fuel source within any of our lifetimes. There is simply too much demand for the product. Because of recent changes to many building/fire/municipal codes, bulk propane may not be available in many locations, especially in areas of high population density. Refilling bulk propane tanks is a major fire hazard. Hint: Don't run out and try to buy bulk propane in population dense areas because you'll pay much higher prices there if you can even find it. Think . . . . truck stops/industrial gasses/farm supply/private RV parks/camp grounds. That implies lower density commercial/residential activity.
Chum lee