China will not be selling any flanker variants to anyone, including Pakistan. That's the deal they've made with Russia.
Options left to Pakistan are more jf17 instead, which is something they could do at any time but wanting a larger plane as well is benefitial, hence f16. So i'd say even without future f16 they will still want to add something else alongside their jf17.
Chinese J10 is an option, especially now that we're seeing it more and more often flown with chinese engine. It might be just a few years away.
Mig29m is also an option, with the ruble as low as it is - it's a cheap option and offers some commonality with engines (jf17 and mig29 both sharing same family of engine)
Modern flankers are possible but they're also more expensive (possibly more than j10, even with the low ruble).
There might be more options a decade down the road but its too far away to talk about them.
In my opinion, it's a fight between mig29m and some export variant of j10.
