For all the wsippel interesting investigations concerning the GPU since a few days:
From what i can say, there were changes made on the GPU well after June 2011. Now, are we talking about "small" tweaking like boost of frequency, or more intricate modifications that concerns the chip design, i don't know. Is it possible for Nintendo to add a feature (like an improved tesselator), add more SPU, etc, without having to change the GPU too heavily, the board circuitry, bus, all the other components even slightly (because i guess the result must be balanced) ? And if they weren't satisfied and/or under the pressure of developers to boost the hardware, is it possible for them to choose another version of the GPU rather than trying to modifying it too much, this "late" in development ? In regard to videogames history, they can, but i don't know if it's the case here.