its probably not that China can't produce enough aircraft, more like after all these reports of catching up.. perhaps it was too optimistic and they need new technology.
but Russia shouldn't go through with it..
unless they want to see the emergence of a new J-11X
and fanboys defending it saying, its not an IP violation, Sukhoi didn't object! its original!
plus, if the su-35 ends up being a 4th gen aircraft with Pak-fa systems, I'm sure the Indians won't like it much either.