Like the people who said the DC-3 would be obsolete 10 years after WW2, don't tell Buffalo Airways.
There's a ton of birds, big and small, still flying from the 40s. The piston engine isn't going away anytime soon. Fuel might get more expensive, but it will be quite a few years down the road before it's really an issue.
Electric planes might be cool, but the thought of having to overnight just to refuel won't sit well with most.