Double Layer 8x drives


Im looking at buying the fastest double layer drive out there. I heard DL 8x is coming soon. Does anyone know if they are already out??
Im happy with the 16x speed for ±r but really want 8x for DL

If I buy a 4x (should 8x not be available), what are the chances of updating the firmware to get to 8x - is this physically possible to double the speed via firmware?