It's a bit unnecessary to invent three scenarios and choose which is the most likely.
There is no reason to believe the NSA is involved. The article does not mention it and there is no other official reason to think they are. The FBI have their own cybercrime unit.
But if the FBI investigation actually did conclusively show that NK was involved, what could they possibly have to gain by putting out a press release? To let the hackers know that we're on to them?
The only possible reason for a press release at this time is to widely circulate this piece of information, which must be valuable to the FBI for some reason. There's no need to complicate the issue further.
There is no reason to believe the NSA is involved. The article does not mention it and there is no other official reason to think they are. The FBI have their own cybercrime unit.
But if the FBI investigation actually did conclusively show that NK was involved, what could they possibly have to gain by putting out a press release? To let the hackers know that we're on to them?
The only possible reason for a press release at this time is to widely circulate this piece of information, which must be valuable to the FBI for some reason. There's no need to complicate the issue further.