I'm guessing Block II aircraft will be the first ones slated for combat purposes. I wouldn't be surprised if J-15 production mirrored that of the Super Hornet, with the first block mostly utilizing technology siphoned from the F/A-18C and the 2nd block incorporating newer components (e.g. AESA radar and EW equipment).
I do believe J-15 will eventually be upgraded with newer avionics in the same way that Block I super hornet was upgraded to Block II.
However I'm not sure if the "block 2" J-15s that we see (aka production serial number 20x) necessarily has newer avionics... I wouldn't be surprised if they are simply the second batch of J-15s -- in other words, what Deino called "block 2" should really be called "batch 2," and what you believe to be "block 2" J-15 (having newer avionics) may warrant a whole new designation. For instance, the true J-15 with upgraded avionics may be called J-15B, having its own unique suffix. A notional J-15B may also be developed with catapult launch capability.
I also disagree with the idea that J-15s which lack the newer avionics would not be combat capable -- J-15s with J-11B level avionics would be perfectly suited for capable, even if they are not as advanced.