Here's an edited re-post of my thoughts regarding the reported deal, first expressed on 03-08-2012:
I can suggest a fundamental basis for a Chinese interest in acquiring the Su-35.
The Su-35 is the ultimate Russian evolution of the T-10 platform which is the basis of more combat aircraft variants currently evolving in the Chinese system than is any other aircraft. These variants include: the J-11B, BS, J-15, and J-16. With this many resources invested in the evolution of this platform, and with the investment going forth into the foreseeable future, I don't think it unreasonable to consider that the Chinese would be interested in obtaining access that would allow them to achieve detailed examinations of adaptations that the Russians applied to achieve their ultimate evolution of the platform. This would allow them to conduct comparative analyses of the Su-27 platform evolution in the Russian and Chinese systems and could provide technical information useful to their ongoing evolution of the platform.
My 2 cents!