By the way, this was the original rumor that spurred all of this buzz:
The guy is a major J-20 watcher and lives in Chengdu. This is probably legit.
Block III will level the playing fields against all of PAF adversaries
Let's tone things down a bit; it'll be a good counter for IAF's Rafales
I wouldnt even go that far. In 1v1 the Rafale+Meteor would wreck the Block III in BVR. In WVR, with HMDS, the Block III might equalize, but it won't get that close unless the Rafale makes a mistake.
The point of the Block III is not to challenge the Rafales head on. It was designed to overwhelm IAF's legacy 4 gen and work in groups to challenge higher threats. The Rafale will need to be countered with tactics, groups of Thunders and Falcons setting up traps. It will take a combined effort with AWACS, intense ECM, and UAVs swarms, especially with S400s on the ground.
This will be the situation all the way until Project Azm comes online. Which is why we need the Block III mainstreamed asap, so we can start shifting resources to Project Azm.
I would imagine that the Block IIIs would be open to integrating new AAMs in the future, in particular the PL-15 and whatever Chinese Meteor equivalent is in the pipeline (PL-21?). From an electronics standpoint the Block III is actually quite a wedge in the IAF's technological advantage, but the Thunder is very deficient in terms of payload, range, speed, and general maneuverability.
But now we are just fantasizing, and not working off validated data. If/When there is any official confirmation that the Block III is getting the PL-15, then we will shift the calculus and re-evaluate. For now, we have to deal with what we know, and that is a Block III with the SD-10.