The real tricky part is, they don't know what could happen tomorrow, let alone know months ahead. So lets say NBA came together and decided that they will have a set spesific period of time for this, lets say month of August to come back and play, well that doesn't mean that it will definitely work, maybe by june or july we will get better, and suddenly on August there is another big spread increase all of a sudden? Is there a guarantee that it won't happen? This is a global pandemic virus, it could go away and come back at anytime, it will NEVER be totally gone, it will always linger, there is no scenario where there is zero infected person on earth. Which is why we need to first make sure we have the cure for it, and if we don't, all the "plans" are for nothing because it may not come real when that date actually comes.
That is the risk the NBA have to think of. They are not really confirming an exact date because just like everybody, they doesn't really know what will happen in the future. I'm sure the officials already think of it and the best that they can do is to weigh a decision that is less risky.
The virus will stay for months or years so I think it is best to play without the audience if they are going to continue in a few months(without the vaccine). What I am thinking is the safety of the players. Basketball is a contact sport. Would all the players self isolate after playing with other teams? Would a team all stay in a quarantine place(for example) during the season. How would they know that a player doesn't have the virus, would they get tested once in a while. Because if one player has the virus, the NBA will be fuck.