I don't think the Malaysians even have access to the black box.
The last time I heard about them, the flight data recorders of MH17 Boeing were being transferred to the Malaysians. That was almost one month ago. But after that, there has been no announcement from the Malaysians. They are refusing to say what was in the flight data recorders, and are not yet ready to release the information public.
I may have missed that announcement. Regardless of if they have it or not, what information do you expect to get from the black box that could potentially be useful to the public? Black boxes do not record the kind of information that would show how the plane was shot down. It is my understanding it only collects information about the performance of the plane (speed, altitude, fuel levels, engine performance, how the flaps are positioned, ect.).
There is a lot of useful data in the black boxes. There are two of them - one is the Cockpit Voice Recorder that records the following on separate tracks: pilot and co-pilot mics, ambient cockpit mic, the speech from both VHF radio trancievers. Then there is the Flight Data Recorder that records what you mentioned above, plus the cabin pressure and information about the radio transceiver engagement, and more. All that information is supplemented with a timestamp track, so the exact time of each event, as well as cross-referencing of the two boxes is possible down to millisecond.
If the plane was hit by a heat-seeking missile, you would first notice an engine failure (engines emit most heat and will get hit first), followed by loss of performance, but the cabin would probably remain intact. It would be interesting then to hear what the pilots had to say during those critical moments. Did they have time to transmit Mayday, mayday, mayday or Pan, pan, pan on 121.5. The tower would have picked that up (the withheld ATC tapes).
If the plane was hit by a BUK, you'd have loss of air pressure in the cabin, but the engines would probably still run for some time.
Finally if the cockpit was shot with 30mm armour-peirceing gunfire from a Mig, then the pilots would be dead within seconds, but the avionics would be intact. You'd also hear telling sound on the cabin ambient sound mic channel.
There is a lot of information that can help you reconstruct the events down to a millisecond, and the sequence and characteristics of events will determine what the cause was.