If China really wants to, I think it's just a matter of time. Their (PPP-adjusted) GDP is 6.5 times larger than Russia, so they can afford to spend a lot of resources on it if they wish.
It's not a matter of time, since Western (and Russian) engine manufacturers aren't standing still. The WS-15 has been in development for over 25 years, and still isn't ready for primetime in the J-20.