Buying on loans is not a wise idea, especially as we are already over extended in our debt to the Chinese. Couple that with the fact that J-10 brings very little incremental improvement over JF-17, it does not make sense to buy just for the sake of it. If PAF was in desperation mode, it could just start building 24-25 JF-17s locally to fill any gaps. But that is not the case, most likely because PAF is going to utilize the airframe life that is left in the F-7s, Mirages and T-37s etc, and go for newer aircraft as they are needed. Remember, a penny saved is a penny earned, and in Pakistan's case, we need to be very stringent on new purchases with our forex, regardless of how we feel and want to counter IAF acquisitions.
PS I am still not over the fact that PLAAF did not buy its share of FC-1s as was intended, to bring down unit costs.