It is much, much more likely that the FBI is pointing the finger at North Korea in the interim while they actually try and figure out who did this. The reasons

It is much, much more likely that the FBI is pointing the finger at North Korea in the interim while they actually try and figure out who did this. The reasons are many: * It might make the investigation easier if the culprits think that the FBI is looking at NK and thus are less careful than they might otherwise be. * NK is an easy scapegoat. If the reality is that the perpetrators cannot be uncovered, the FBI looks more competent by pointing the finger (unprovably) at NK than saying "We have no idea." * The FBI doesn't care if NK actually did it. If they can merely tangentially prove that NK was involved, it prevents a massive security breach from being an unsolved crime. To have a breach the size of Sony's remain unsolved would bolster every would-be hacker in the world.