All the 4th , 4.5 and 5th generation marketing confusion terminology aside,
which of the current or future Russian or Chinese platforms poses any real treath to the Western fighterr ?
Honestly ,the Mig29 /SU27 and all of their derivatives never had anywhere
near the upperhand against most, if not almost all of their Western counterparts.
I would make an educated guess that with all the possible future upgrades of
'4th generation' fighters with regards to Radar, ECM, ECCM, Networking, engines, etc.... , the latest Flankers or even their PAK-FA or J20's still won't
bridge the gap that has been there post WWII.
The most significant threath that now exists is in the fact that technological information and equipment is now ,more than ever, available on the open market and can be reversed engineered or just implemented in almost all fighters regardless where they came from, no amount of F35 wizardry will change that.
As an example just look at what the IAI can do with a 50 yr old MiG21, after they are done with their upgrades it still is a very potent and dangerous adversary.
For us on the other side of the pond it is now time to put our eggs in our own basket and finnish what we started, the Rafale and Typhoon have to be developped to their full potential and both get their necessary upgrades, it would leave us with a top of the line platform that could keep us on top till 2030-2040 when we could invest in their successors , in the meantime catch up a lot of potential export orders.
This is by no means an anti american move but we shouldn't invest in the folly that is the F35, this is not the next F16-18, it's more like the next F104 and we all know what a miserable failure that was (also LM BTW).
Enough good US hardware we could invest our ever shrinking budgets in, the P8-Poseidon, B737AEW, C17, Chinooks, V22's,.... all make enough sense to be considered .