I've worked on 13 Olympics since 1984 so happy to answer any sports related questions. Previous comments about some accommodation and tickets being cheaper closer to the Games are valid but remember that these Olympics will attract Japanese, Chinese and Koreans to Japan as well as the rest of the world so I expect heavy demand for everything.
If you wand to see some new (returning) Olympic sports look out for Baseball/Softball, 3x3 Basketball, Sports Climbing, Karate, Skateboarding and Surfing. I can see some Aussie medals there.
You do need a lot of energy and patience to attend any Olympics (or lots on money) but I think the Japanese will be better than some other countries and are very well organised already from what I hear.
And to add to the last comment; the Olympics must finish before the NFL season starts in the States - yep - TV does influence the scheduling.