There is no replacement of aircraft.
There is fulfillment of roles.
The PAF needs a strike element capable of large payloads. A platform that is survivable, easily serviceable and integrates with existing doctrine.
It needs a fighter capable of evading the Indian Air Defence environment deep enough to strike at the targets well inside India with standoff munitions, and then be able to egress out with a high probability of survival to repeat the process.
The XL is a dead program - so is the premise of this thread.
The perfect replacement for the Mirage 5 is the Mirage 2000, and that chapter is closed as well.
The only options open to Pakistan with its current economic and diplomatic situation is to continue upgrading the JF-17 to be a more effective multirole payload whilst simultaneously buying one or two additional squadrons of Block-72s. The rest of the focus is on a 5.5 gen fighter.
These aircraft will then balance and cooperate on these roles until the PAF is able to generate or procure a platform that does the above stated mission.