Maybe not ITER (or even DEMO), but specifically nuclear fusion becoming a viable practical energy source.

I went to JET last year, which was amazing to see, but I couldn't help but get the nagging feeling that we won't see tritium/deuterium fusion hit mainstream within our lifetimes.

Mind you, once it does reach mainstream that will change everything. Hopefully there won't be a race to mine helium 3 from the moon.