I think this is an interesting point. Anyone have any ideas when this might happen?
A few ways this could happen:
1) If enough games are lost that there becomes significant doubts that the league will ever come back. I believe that's a very late condition. Probably when the second season is on the verge of missing games. If the risk that two full seasons would be lost became appreciable it would be reasonable to believe that there is some significant risk that the NBA as presently constituted will never return.
2) If an alternative league is formed that appears to have a legitimate chance of sticking.
3) If it becomes apparent that the NBA begins losing stars to foreign leagues in a more permanent way. (Think if Lebron signed a 10 year contract with a Chinese team with no NBA outs for example, that would significantly negatively affect the value of the Heat).
4) If any single franchise folds entirely or an owner publicly requests that his investment be cashed out by the league.
All of these are not imminent conditions, but they serve as reminders that the current popular narrative of "the longer this goes the more pressure shifts to players" is untrue to the extent it reflects a one way street. Once an entire season is cancelled the primary costs of the lockout are already effectively locked in on the players and the game from that point on is one in which owners are probably fighting for a personal $300-500 million asset.