I've said it before, and I'll say it again, a stealth JF-17 is impractical and expensive. It's easier (and cheaper) to buy the FC-31, or develop a brand new one from scratch (which is also expensive to do).
Right now, Pakistan isn't in the financial situation to do any of these things. There may be reports that Pakistan is interested in the FC-31, but that doesn't mean Pakistan is going to buy it right now. Pakistan is playing the waiting game, their next acquisition will depend completely on regional air forces, such as India. If the IAF buys the Rafale, Pakistan may buy more second hand F-16s and start thinking of shopping for a 5th gen fighter, but only after the IAF has inducted the Rafale into their air force. The biggest turning point would be when India inducts the FGFA, when Pakistan will have no choice but to buy a 5th gen.
The time frame for any of this is 2020-2025, plenty of time.