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I wouldn't say so. If you watched sports competitions from Japan recently, you would see that they already allow fans to watch it, offcourse only limited numbers. So, if situation won't become significantly worse in Japan until July, I think we will see some spectators allowed to visit events.
I am not following Japanese sports and if they started allowing limited number of spectators then we can assume that it is possible with the Olympics as well considering we will not see a second wave like we are seeing in other countries.
Question, will they allow foreign tourists to watch Olympics, I think it's less likely.
And even if vaccine will be fully developped until next dummer, there is no chance that huge part of population will be vaccinated until Olympics.
The situation will determine whether they allow foreign tourists and if they allow they will be living in a bubble with ample testing and other procedures and vaccinating everyone is highly unlikely but if the Japanese government wants to spend money on that or the tourist coming in can pay for the vaccine it is possible for everyone visiting the Olympic village gets vaccinated if a proper vaccine is developed by that time.