The diesel-electric locomotive could dominate railroading for as long as the earlier steam locomotives, but there are some possible alternatives. They include electrification and dual-fuel locomotives. Real breakthroughs will require long-term committment and financial help from railroads.
There are challengers, but they'll need massive investments that aren't now in sight.
The diesel-electric locomotive seems as secure today as the steam locomotive must have seemed 120 years ago. Then, ...