China will have more than enough J-20, J-16, J-11, J-10, and UAVs to deal with conflicts involving its immediate neighbors. The J-31 would be overkill. The only real concerns for China are distant threats posed by the U.S. and Japan. The PLAAF will need combat aircraft with long legs that can support the PLAN and can keep the massive U.S. Navy at bay.
The J-31 isn't it. It's a medium fighter unlikely to have enough range to keep up with the flankers and the J-20. I suspect that production of J-10C was halted for this same reason.
I expect the J-31 will be an export-only variant, with avionics appropriately downgraded for reasons of operational security. I doubt the J-31 will ever be inducted into the PLAAF.