With a dual engine failure:
-there's time to get a mayday
-there's time to get a 7700 out
-you'll enter a fairly shallow descent if there's no fuel, a slightly steeper one if there is fuel in order to try a restart. There's no plunging involved like this plane.
-glide distance in still air will be about 70+ miles
-you'll be turning the aircraft away from high ground, this aircraft went straight on
-there are flat dried river beds in the area, no way would you head for the hills for a forced landing
As it stands, there's no evidence of any of these occurring and in my opinion there's no evidence of a dual engine flame out.
We have the aircraft in two parts which to me suggests an inflight breakup. What caused that and wether it was internal or external is unclear at this time. I can find no evidence of severe weather and the plane won't just fly iteself into coffin corner with gay abandon like others have suggested so speculation about it being too heavy or above the max alt is pretty fruitless.