I think they're making more and more sense with time
GK stands for Kepler architecture as GF stood for Fermi and GT for Tesla (and thus we can infer Maxwell codes will start GM), so its actually easier to tell whats in the GPU from the code name than the actual product number (for instance, many the really low end GeForce GT 600 cards are using GF108 and 119 GPUs...)
Then there's the number designation, where in the short time we've had them they've denoted class of GPU:
100
104
106
etc
where the ones column represents pecking order (ie 104 > 106), the tens column has come to represent a revision (ie 114 newer version of 104), but they haven't done much with the hundreds place so far, so it'll be interesting to see what this might mean as they finally start to get some more concrete structure to their codes.