I just don't buy it. It was a far-fetched scenario in the first place. 99% of the time if they didn't steal money it's just some people doing it for the lulz. Of course they'll pretend to be North Korean. That's the funniest explanation.
Yeah, I can imagine the hackers releasing a torrent of the interview on the date it was supposed to be premiered before Sony got on their knees. With a simple message accompanying the movie: "lulz, trolled u".
But getting hacked by a couple of kids or a disgruntled employee sounds like you may have not taken good care of security, whereas getting hacked by a sophisticated, evil commie cyberarmy is something you could not have avoided. Who cares that, by saying the latter, Sony is fueling the war machine.. I really hope that your scenario turns out to be true.
It's a plausible explanation. However, I wonder if the lulz is really worth the risks they're taking with something of this scale. Even for a reckless person.