Well, if you know how to desolder large BGA chips, rewire the supporting circuitry, and program a new driver, then yes, you can upgrade your graphics!
Seriously, many people on these boards still do not understand that Apple laptops have graphics *chips* in them, not graphics *cards*. The chip is soldered to the main logic board (MLB) and cannot be removed or switched without replacing the MLB. I do not believe any Apple laptop ever allowed upgrading the GPU. There is no space in these machines to have such an upgrade option. I thought I heard that some PC laptops may have this, but think about how big and heavy those machines are compared to ours.
Steve