I still believe that the parts to be produced using the mold will not be molded directly into it. Some of the holes that were drilled into the block in fact serve to fix the inserts which will form a crude which is then machined housing (finishes) using a CNC milling machine. Thus, and assuming that my theory is correct, the dimensions of the box will be determined by the widest part and not the bottom of the mold.
The site superimposed an iPhone 5s to fit the mold and measured the new screen size at exactly 4.7-inches. This is exactly the size widely rumored for the next generation device.
If the boxes iPhone 6 will actually be manufactured using the mold and assuming that my calculations are correct, this model should measure approximately 138mm long by 64mm wide and be fitted with a screen of 4.7 inches.
Take a look at the photos below. If you have any expertise in these molds please let us know in the comments.