You know what Pakistan's policy is, if India tries to take Pakistani Kashmir? Nukes!!!
Now does it occur to you that India has nukes as well?
Even if, in your hypothetical scenario, Pakistan grows militarily and economically stronger than India (which means Pakistanis have to be 7 times richer than Indians per capita and several times militarily stronger to make up for geography), do you think India would simply let Pak steal one of our states, and keep our nukes in cold storage?
Whether you like it or not, India is a military and economic power, and a nuclear power to boot. Nobody will steal anything from India. Two generations of Pakistanis have ruined themselves chasing the Kashmiri chimera, and I don't know how many more generations have to deluede themselves with that pipe dream. Taking territory from a stronger, bigger, richer country is impossible in the real world, unless you convince yourself of the old "ek mussalman = 10 kafirs" theory.