After 60 years I’d suggest they no longer “show promise”.
After nearly five billion years of heat from Sol, I’d say hot fusion show plenty of promise.
His talk was a marvel. This was well after the time where power-point presentations on a memory stick were the audio-visual norm. He showed up with a set of transparencies a good six inches thick. I had to scramble for an overhead projector for an auditorium otherwise fully tricked out for light and sound. He talked clearly and coherently at a mile a minute while pawing through his stack of slides selecting about one out of six to actually show.
It was a marvelous talk, easily in my personal top ten. At one point he paused and said something to the effect that he was going to tell a story that he didn't want to leave the room. It involved DARPA and it was damn funny. Say no more, say no more.