To be honest, although i see myself as a hardcore russian fanboy, reallistically i can't see them flying their RAD 6th gen much before 2030 even under the best circumstances, and be in service much before 2040s, so it will make sense for Russia to buy some CHADs, either J-50 or perhaps the J-36 given russian range requirements, as an interim solution in say the second half of the 2030s. Just like China bought Su-35 the previous decade.
The problem for China MIC exports to Russia is that there are few items Russia can buy without undermining its commitment to self-sufficiency. China can buy a few S-400 batteries or a few dozen Su-35s without serious implications for its own MIC objectives (indeed, many would argue that those acquisitions are ultimately intended to benefit China's own MIC). Russia's defence-industrial situation is much more precariously balanced on the edge of sustainable self-sufficiency in terms of research, development, supply and demand. Russia's post-Cold War issues in the development and production of modern systems are fundamentally problems of long-term demand: the orders just weren't there to keep the factories and assembly lines running, maintaining the skilled workforces, let alone investing in tools enabling modern production techniques. Considerable effort was made to preserve high-level expertise in strategically critical fields such as aerospace, nuclear submarines and nuclear forces and we have seen both the impressive fruits and real limitations of those efforts. In a very real sense, any order from China is an order that doesn't go to maintaining Russia's own MIC. You are trading off short-term capability benefits against long-term strategic autonomy objectives, and that is a trade-off that will rarely survive scrutiny, and almost certainly would not do so in the context of future PLA combat aircraft.
That isn't to say that all such efforts are futile, however. One opportunity is in the short-term provision of items that are experiencing temporarily elevated levels of demand, such as all equipment and munitions that Russia is chewing through in Ukraine. For better or worse, such opportunities have been largely foreclosed by China's decision not to directly support Russia in that conflict. Another opportunity is in relation to small-scale procurement of specialized capabilities that are within Russia's technological grasp, but are simply uneconomical to pursue, as with the French use of American E-2D Hawkeye for carrier-based AEW. France could build their own system, but does it make sense to do so? But the most compelling opportunities for cooperation would be those that actually align with and reinforce Russia's long-term MIC objectives. Despite vociferous criticism from Russian nationalists, that's really what the now abandoned
Mistral deal with France was about. The ships were the price to be paid for French assistance in rejuvenating Russia's naval shipbuilding sector with modern production methods. Needless to say, China too has a lot to offer Russia in the art of
building stuff better. Of course, any such arrangements would have to work for China as well.