OK, to add my own answer, instead of just commnenting.
Ummm... to start with "what everybody else has already said." If I have anything to add it might be (and somebody might have said this already as well, and I just missed it)
Synthetic Biology - this entire field fascinates me, and I expect big things to come in the future when we can customize DNA and grow items we need, that are tailor made to various parameters. This is also the beginning plot-line to many horror novels and movies though, so "everything isn't rainbows and sunshine" as they say.
Nanotech - related to above, but as with synthetic biology, it fascinates me to think what we can do when we have atomic scale self-assembling machines.
AR/VR - maybe not "under the radar" anymore, but I think there's a ton of untapped potential in this space.
Semantic Web - Yes, I'm still a believer in the idea of RDF / SPARQL / etc. I've said enough about this in the past, so I'm not going to drill any deeper here.
AI - maybe more "AGI" than the ML stuff we have today that gets labeled "AI". And saying that is not an attempt to denigrate ML or any of the radical stuff going today. It's just that for as much as contemporary "AI" can do, I think there's a lot it still can't do, and I like to daydream about the potential of AI's that get closer and closer to (and exceed?) human abilities. See above about horror movie plots though. :-(
Fusion: this has definitely been mentioned already, but add me to the list of people who are hopeful/excited about the prospects.
Time Travel: Actually no. I kinda hope this is impossible. I have a feeling that if unrestricted "Doctor Who" like time travel was possible, causality would collapse and all of reality would just become a big, jumbled mess, incapable of supporting life.
Ummm... to start with "what everybody else has already said." If I have anything to add it might be (and somebody might have said this already as well, and I just missed it)
Synthetic Biology - this entire field fascinates me, and I expect big things to come in the future when we can customize DNA and grow items we need, that are tailor made to various parameters. This is also the beginning plot-line to many horror novels and movies though, so "everything isn't rainbows and sunshine" as they say.
Nanotech - related to above, but as with synthetic biology, it fascinates me to think what we can do when we have atomic scale self-assembling machines.
AR/VR - maybe not "under the radar" anymore, but I think there's a ton of untapped potential in this space.
Semantic Web - Yes, I'm still a believer in the idea of RDF / SPARQL / etc. I've said enough about this in the past, so I'm not going to drill any deeper here.
AI - maybe more "AGI" than the ML stuff we have today that gets labeled "AI". And saying that is not an attempt to denigrate ML or any of the radical stuff going today. It's just that for as much as contemporary "AI" can do, I think there's a lot it still can't do, and I like to daydream about the potential of AI's that get closer and closer to (and exceed?) human abilities. See above about horror movie plots though. :-(
Fusion: this has definitely been mentioned already, but add me to the list of people who are hopeful/excited about the prospects.
Time Travel: Actually no. I kinda hope this is impossible. I have a feeling that if unrestricted "Doctor Who" like time travel was possible, causality would collapse and all of reality would just become a big, jumbled mess, incapable of supporting life.