That's India's problem.
Plebiscite is the main, best way possible and forward, for Kashmir, from Pakistan's stance. Otherwise you can expect war at any point, at some point, in the future.
Another solution, which could work is a unified Kashmir wherein there is no border between Pakistan and India, the citizens can choose to have either Pakistani or Indian citizenship, and likewise the Government is a joint Government, and it is administered jointly with free crossings. Since Kashmir is the core of all problems between Pakistan and India, it will bring an end to trouble.
I don't see anything else. Some people say that declaring the current boundaries as international border is a solution. I don't think it is. It doesn't solve the problem in essence at all, that is who Kashmir belongs to.