Based on the pictures posted here and here, it appears that the sneak preview R4-G9 figure has some elements that were created for the VOTC R2-D2.
The centre leg looks as though it is removable. If it is not, then Hasbro did a remarkable job in making this thing retract all the way inside the droid.
The new figure also has separately moulded "wires" for its main legs. I'm hoping that these features become standard design for all forthcoming astromech figures.