From what I understand 6th gen will add more sensors, direct energy weapons, optional unmanned operations, more sensor fusion all these things can be added to 5th gen as well if there is space and power available. But what it will bring new technologies and processes that will simplify...
My guess is that it has Link 17 so it would be able to guide PL15. If it doesn't have Link 17 why would PAF add more Erieye if it can't communicate with it's backbone fighter?
Most likely Erieye does communicate with JF17 thought link 17 as Saab does advertise them being able to integrate custom links otherwise it doesn't make sense for PAF to add more Erieye.
From reading @messiach comments on JF-17 thread I got the feeling that PAF might be interested in J35 but that jet is FAR AWAY from becoming a real consideration even it's engine WS19 is suppose to complete development in 2025 and these projects rarely meet deadlines. But a year or so back there...
I doubt any new fighter will come between block 3 and NGF. I don't think there is block 4 in the works, I mean what can it bring in addition to block 3? Super cruise maybe?