Yeap. AMD did this with its Phenom II chips. Maintain the same fab process for a 4 core processor but sell it as dual or triple core if it was poor quality. AMD motherboards famously had the feature to enable the locked down processors. Obviously your mileage would vary but going from 3 cores to 4 was a pretty significant performance boost especially for the initial cost.

A while back there was a way to unlock an AMD 6950 GPU to a 6970 as well. Had something to do with unlocking some memory modules since the cards were identical.