Glow will be around until something catches it in performance or price. Electric already is very close in power to weight ratio, sometimes better if you don't need a long flight time. But it costs more. Gas is cheaper when you figure in the cost of fuel, but those engines are heavier. Gassers will continue to get lighter, and electric will continue to improve flight times and get cheaper. I give it 10 more years before there is no reason aside from nostalgia to use glow engines.