Re: What can be learned of the crash at this late stage?
Indeed, there won't be as much evidence after so much time and seas.
The "black boxes" (you're right; they're orange) are sealed, durable, and located in the tail of the aircraft to best survive a crash. They're likely intact, and they won't degrade much in seawater. What has failed, though, are the locator beacons. It will be a real pill to find those black boxes now.
The aircraft...probably not much left of that, and they would probably retrieve only a few things. (In shallow water, it would be torn up and dispersed by heavy seas, and in deep water, hard to recover.)
The black boxes usually give enough information to model what happened, and make a theory about why. The Flight Data Recorder logs all instrument data (speed, altitude, fuel, attitude, temperatures, engine parameters, etc),warnings, control positions, and control inputs. That's enough to figure out what they plane did.
The Cockpit Voice Recorder logs all sounds from the flight deck, including conversation, bells and beeps, clicks and swooshes and similar sounds when someone pushes buttons or moves things. If both pilots are chatting about family and then there's a cacaphony of warning bells, that's obviously a different situation than if 1 pilot is heard ranting about Amelia Earhart while there's a muffled banging on the door in the background. Or if we hear labored breathing and 1 pilot asks the flight attendant to find a doctor. If the end is just computer noises, and the pilots were never heard leaving the flight deck, we might remember Payne Stewart.