I think we can do some informed speculation based on some of the information that TSB has released to the press at this point.
TSB has reported that the tail struck the berm at the end of the runway (where it broke off), but there has been no mention whatsoever (at this point) that any of the landing gear struck the berm. So it appears that the aircraft got airborne just enough for the landing gear to clear the berm, but we know that the tail did not. The berm is located about 300 meters from the end of the runway.
The first tailstrike occurred at 250 metes before the end of the runway. Is this close to where VR should have occurred for this aircraft, at it's weight and at the field conditions that were present that night?
The other tailstrike occurred at 170 meters before the end of the runway, and appears to have continued until the aircraft finally lifted off right before the berm. This suggests to me that the pilots were trying desperately to get the aircraft airborne.
The distance between the first and second tailstrikes, may have been occupied with a sudden surprise to the pilots of a tailstrike, followed by a realization that the wheels were still on the runway, followed by a quick realization that they had to get the aircraft into the air. However, only the CVR (and perhaps the FDR) can really tell us this.