Some are as long as 10 or 15. Depends on the agreement. In any case, no NDA is permanent. A court would nullify any agreement that a lawyer positions as such, but in any case, just because a NDA is finite does not mean that when it does end the parties involved necessarily are obligated to tell us anything either.
If the deal failed and those at the table have all moved on to other things, who would be left tell us? NCSoft wouldn't make a disclosure if there's no new business or PR advantage to saying so. And if the prospective buyers don't care to come forward with what happened, how would we know? (Downix might get an answer someday, but he can't force people to talk.)
Not trying to pour salt into the sugar jar, but making folks aware of the expectations.