Looks like the Authentics line will have two sizes, similar to the Cyber series (Battalion & Commander), as a larger sized Optimus and Bumblebee have been found on the Hasbro website (looking like they have the same engineering, but just upsized with a couple extra joints).
The larger size is said to be about 7 inches (about 17cm - the size of a Voyager), and the product numbers match up with the mystery "project storm" items that were leaked a couple weeks ago.

It also suggests that the Authentics Grimlock toy that was leaked a few weeks back, that was assumed to be wave 2 of the smaller size, now looks to be part of this new larger range.