I agree that sanctions are not likely to happen. But this is the case simply because there is no reason for western countries to sanction Pakistan at this point. Sanctions are usually made when there are specific objectives in place. Now that NATO has said goodbye to Afghanistan, there is nothing left to gain.
However, I do not agree this China backing as a reason for ineffective sanctions. You will notice today that Pakistan's primary export partners are the NATO countries and not China. In fact, Pakistan has a substantial trade surplus with western nations that need cheap goods from low income countries. China on the other hand does not have this need. In fact, very few countries have the capability to manufacture goods that are cheaper than what the Chinese could manufacture. Case in point, check the China - Pakistan trade balance.