“Long term” is a phrase that is the opposite of “short term”. When Harrison used this term, he meant that while coal wasn’t going to disappear overnight, it would eventually. He even qualified it by saying this would not happen in one or two years, implying this would be sometime after that.
Any twit knew what he meant. Apparently, you have some cognitive problems.
To answer your question — there are other forms of energy that can be developed to replace coal, and fossil fuels in general. We already use hydroelectric and nuclear energy, and have for decades. Solar and wind energy are fairly new to the game, but their use is accelerating rapidly. There’s also geothermal energy, which has hardly been tapped yet. New forms of energy continue to appear on the horizon, such as the harnessing of ocean tides.
See? I am capable of answering questions without resorting to troll tactics, or finding some silly semantics argument to grasp onto. I guess that’s the difference between us.