Well firstly, I said I think the J10B will be the final major modification of the J10. I never said that CAC and the PLAAF will stop improving on their existing planes and upgrading them throughout their service lives. But those will be incremental upgrades rather than a revolutionary leap like the J10B was compared to the J10A.
As for dedicated vs multi role, as a general rule, I never accept "well everyone else does it" as a valid excuse for why I should also do something.
The vast majority of air forces people tend to include in the proverbial 'everyone else' in this case are western NATO air forces, which for all intents and purposes could be counted as a single case since they all follow broadly similar general philosophies.
Furthermore, all those NATO air forces were built with the expectation that they would be fighting either significantly weaker opponents (Libya), and/or they would be fighting as part of a US led coalition. In both cases, establishing air superiority would never have been an issue.
None of that applies to China, and indeed, when you are building your military with the expectation of having to fight against the world's only military superpower, is it any wonder you come up with significantly different conclusions to those who built their forces expecting to fight alongside the US?
On top of that, there is the vastly different strategic role and position China finds itself compared to the US.
America is an offensive global force who never realistically expects to have to fight over their own soil. When America goes to war, they go to war far from home usually without deploying ground forces, so pretty much all their offensive firepower has to come from the sea or the air. That is why its important for every fighter to be able to engage ground targets.
China is still a locally defensive power, and if China does to war, it will be fighting mainly over its own territory, or extremely close to it.
In a primarily defensive war over Chinese territorial, what does multirole capability add to the PLA? I am, of course ruling out the scenario of a foreign invasion of the Chinese mainland as I don't think anyone has the capability to seriously contempt it, never mind hope to be able to pull it off.
Even in a war in China's near abroad, just where would the PLA realistically be fighting that would require it to have a full multirole fighter fleet as its primary offensive means? Against any of China's land locked neighbours, the PLA will be bringing the big guns and delivering the hammer blows. All of China's maritime neighbours are either too far away for land based fighters to be of much use, and/or are US allies and the PLAAF would need to defeat the USAF/USN in addition to their own national air forces before they can even think about engaging ground targets on a large scale.
Even in a Taiwan scenario multirole fighters would be of little use since the PLAAF will not have the luxury to systematically bomb the defences to dust before sending in the grunts. Any Chinese invasion of Taiwan would involve an overwhelming missile strike by cruise and ballistic missiles followed by a massive amphibious invasion as soon as the PLAAF achieves air superiority and clears the landing sites, after which the PLA would, again be delivering the primary hammer blow. At that point, the PLAAF would probably have to gear up ready to fight off a US military intervention rather than help the ground pounders take the island.
Multirole might be nice and all fashionable, but its not really all that important for the PLAAF at present or in the near future.
