How much basis in reality does the speculation on J-15/J-16 production lines stopping to accommodate J-35 production have? This sounds incredibly far-fetched.
I'm not sure who has speculated that, but overall SAC has seen some expansion of production capacity even before that big new facility they have built.
It's not unreasonable to say that aircraft production footprint is finite therefore they have to build a mix of different aircraft in any given footprint, but the idea that the entire production of an aircraft type has to be "stopped" to produce a new aircraft type, is a gross oversimplification.