Cool. A.I. will be in a better shape in 4 years, and it'll be cool to have simple interactions with advanced robots to showcase their capabilities. It'll still be a gimmik by 2020 tho.
Instant Language Translation apps
We kind of have that now. I bet it'll be a mature tech by 2020, and such an international event is a perfect venue for that.
I don't know about Japan's regulatory framework around autonomous vehicles, but this is certainly possible by 2020 since we're almost there technically.
8k TV Broadcasts(7680x4320 resolution)
Pointless. I disagree with alt13 about 4k vs 1080p, but almost nobody will have 8k TVs by 2020. 4k will be the norm by then, however, and it'll be nice to watch the broadcasts at that resolution. Speaking of alt13, do you remember when you said that 4k TVs will go down the same route as 3D TVs and not catch on? Hah.
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Hydrogen powered villages
Whatevs.
Artificial Meteor Showers(Satellite shoots chemicals through atmosphere, burning like class 3 meteorites)
Never heard of this before. Sounds expensive. Doubt it'll happen.
Superspeed Maglev Trains(up to 374 mph)
I assume they have this now? Right? If not, then it's at least being constructed? These things take time. Not like you can do it in a couple of years.
5G networks(theoretical standard, demonstratable 2 gigabits/second)
We will certainly have 5G in the deployment phase by then, or shortly thereafter. It is plausible that they will have the technology in small areas in the relevant locations, and that can act as an accelerator for widespread deployment in the following couple of years. It is also the most useful technology on the list.