The Chengdu J-20 is a 5th Generation MRF which is envisioned to be Communist China's answer to Uncle Sam's F-22 Raptor. Unlike the Shenyang J-31, this stealth aircraft will not be made available to the international market (hey, just like the F-22 too).
US warfighting whiz kids believe that the J-20 will be more than a match against any 4th Generation MRF (e.g. F-15, F-16, F-18, Gripen, Rafale, Typhoon, etc.). Accordingly, only the F-35 and the F-22 will theoretically be able to dominate it.
If deployed in Communist China's fake islands in the Spratlys (specially Mischief Reef), the entire Philippines will be practically within its range, without any aerial refuelling. And its stealth capabilities will enable it to elude most air defense radars.
It is expected to be deployed in 2018. That's only two (2) years from now. And is suspected to be currently in the low production stage.
The PAF will have to take into even more serious consideration the Chengdu J-20 in determining its choice of MRF.
Who would want to spend a small fortune on an MRF that will already be obsolete against its expected adversary just two (2) years from now?