From what I read, they are suing not because the players are going to shed their union status, but because the players (or their lawyers) were using the threat of that (which would be a sham) during negotiations the other day.
If that is actually what happened, then I think the league has a decent complaint there. That would certainly not be a case of the players negotiating in good faith.
But anyways, there is no way this happens. If the judge rules in favor of the owners, and says that if the union decertifies, it has to be the real thing, which would wipe out contracts that were attached to the Union, then there is no chance the players decertify.
The league is kind of doing the players a favor by doing this now, because had they waited until after the players decertified, and the judge ruled that way, the players would be screwed. This way they can make the decision on whether to decertify knowing how big of a risk they will be taking.