Don't most nda's have an expiration date? If talks have stagnated, it'd be nice to definitively know, instead of just making the assumption based on the very overwhelming, empirical evidence that NCSoft manipulated them into hushing all of us up.
In my experience yes, most B2B NDA's do expire at some point or under specific circumstances relating to the subject of the NDA becoming public knowledge. Arcana points to some specific cases where the NDA would never expire. Those tend to relate to knowledge of IP that is trade secret.
I've not seen an NDA that precludes the parties from never disclosing that negotiations have ended, but I've also not dealt with a Korean software company. They may have a different take on business negotiations and NDAs.
Also, I could imagine that the NDA might include a relatively short cooling off period (e.g. 6 mos. to a year) prior to a party disclosing that negotiations have broken down. That would allow one or both of the parties to come back to the table before any announcement that the negotiations have ended.