J-10 is impossible now and J-11 is unlikely due to license issue. An aircraft that can give PAF a lead from IAF can be a 5th gen aircraft like J-31. Still, at some stage F-16 has to be retired or replaced so an aircraft which has formidable capabilities in future is either EF or SU-35 with significant technology leap.
Even if EF is pricey, PAF can start inducting it in small numbers like 12 per squadron, starting from 24 making 2 squadrons and increase a squadron every 5 years. No one knows about budgetary situation of future but a first step has to be taken. SU-30 is flown by IAF so getting a similar aircraft like SU-35 might not be the best decision.
Against the likes of Rafale and SU30, PAF needs a suitable adversary aircraft. Even after inducting J-10B ,PAF would need another aircraft which can give a hard time to the enemy. J-10B may have modern gadgets but it will not be able to give IAF a hard time that an EF can certainly give followed by a 5th gen.
Suppose PAF can spend $5 Bn, its better to spend it on the best available aircraft out there, rather than losing it on J-10B and still needing another aircraft.