We may never know
As the aircraft stayed airborne (and under positive control of the crew) long enough to run-out the CVR, we may never know what was going on up there. I like the idea of securing and investigating the laptops; that would provide some conclusive data provided they were confiscated at landing (doubt the crew would have time to fudge anything on the laptops once they were busy trying to recover from the gaff.) However, I haven't heard anything in the news about the laptops being a part of the investigation.
I think these guys will get off light..."distracted trying to figure out crew scheduling" (while still quite frightening to the world)...sounds better than "Fell asleep" or "just zoned out..."
Just my two cents.