i bet it's a $299 ps3 with Backward compatibility

faster speed (4x or better), smaller diode Blu-ray drive perhaps?

Unlikely.  Movies don't really need it, and developers wouldn't be able to utilize the extra speed for games (outside of installs), so it wouldn't have much use and would only add to the cost of the machine.

Dualshock sounds realistic. I would think they would make a new SKU together with the 65nm GPU sometimes this fall.

The best thing they can do is replace the 40gb model with a 80gb model.It should have bc and 40gb more in hdd( it will lack the 2 from the 4 usb ports in the current 80gb model and the card reader).Of course they can lower the price of the 40gb to 299 until inventory runs out,that would also explain the 100 gift card they promoted in June,maybe they gave it to clear faster the inventory and not for mgs4 promotion

Well then again it could also be the 45nm cell and the 65nm RSX ...and lets say a 50$ price drop

Hopefully its something good.

Maybe they will dump Sixaxis (since its discontinued anyway) - and replace that with DS3 + 1 game ( Resistance ? Folklore? some older PS3 game which was received well but is no longer selling ...