In my personal opinion, every thing depends in the events taking place, Su-35BM is already being delivered to the Russians air force in fact 3 new Su-35BMs will be delivered in december 2012, Saturn already has 117S as an engine in production.
Saturn says Type 30 engine will be flown on PAKFA in 2015, by the time Su-35 could be delivered to China, type 30 is a 17.5 tonnes thrust engine, lighter cheaper than 117S.
There is little information about the new engine of T-50. According to preliminary facts, the engine will have increased thrust and fuel efficiency as compared to AL-41F1. Allegedly, the powerplant will have a thrust of about 107 kN in cruise mode and 176 kN in full afterburner mode.CEO of NPO Saturn, Ilya Fedorov, said in April 2011 that development of the new engine is running ahead of schedule and the first engines will be delivered to the Russian Ministry of Defense in 2015. The first serial T-50s should be acquired by Russian air forces the same year.
Комсомольское-на-Амуре авиационное производственное объединение им.Ю.А. Гагарина (КнААПО) завершает лётные испытания первой партии многофункциональных истребителей Су-35С для ВВС России. В полётах участвуют 3 серийных истребителя, имеющие бортовые номера 05-07 «красный». Планируется, что в первой половине декабря самолёты будут переданы ВВС и поступят на вооружение 4-го Центра боевого применения и переучивания лётного состава в Липецке.
three new Su-35 to be delivered in December to the Russian Air force to the Lipetske Air base