I just checked our inventory and see that we still have some K2 matte black, photo black and cyan (and some other colors) in 4, 8, 16 and 32 oz bottles, but are totally out of light magenta.
Yesterday, I checked the data and did a smear test to closely compare ConeColor K2 and K3/Pro inks. The two ink sets are not formulated exactly the same, but based on my smear tests, color and density-wise, it seems that you can smoothly transition to using the ConeColor Pro blacks, cyan, light cyan, VIVID magenta, light magenta, and yellow.
The CCP LK is a bit lighter than the K2 LK, so you will want to re-profile for the best output after installing the lighter LK. I see we still have three 8oz bottles of K2 LK left, if you want to continue using that ink as long as possible.
I hope this helps.
Best regards and happy printing~ Dana