Sorry bro, but i'd have to disagree with you on that.
I know you to be one of the major F-16 fans on PDF (like myself), but though US & most NATO Allies are replacing the F-16 with the state-of the-art F-35, there is no way the US will ever offer us the F-35.
The only way I see the F-35 in the PAF inventory is if the US go out full WAR mode with Iran & somehow get Pakistan involved in it. Chance are slim to none on that scenario.
So, F-16 Block 72 & upgrades on present F-16 is The Best offer we'll ever muster out of the US; and that too will come at a cost - and i'm not talking about money.
Its also been discussed is the past and a new Member also mentioned that US won't be offering India the F-35 because of the S-400 Deal. The US/Lockheed Martin went to a lot of distance crafting the F-21 which they claim to have the F-35 DNA*.
*explained to me by the (former) Test Pilot of the F-16 for Lockheed Martin during the DxB Air Show.
So, I doubt the F-35 to be in conversation for either Nation in this part of the World.
As for the J-20 and the Y-20... China has made it clear that they are not for Export, but one really needs to wonder/raise the question if those rules apply to their all-weather ally: Pakistan