The first guy, the one who wielded a rock, was all but invincible until the second guy figured out how to tie a stick to a rock and turn it into a club. That guy thought he was the cat's ass until he ran into a guy with a longer stick with a pointy rock on the end. The lesson is, when it comes to finding ways to kill each other, breakthrough begets breakthrough.
So remind me why we're looking to spend 70-billion dollars on breakthrough technology purpose built to defeat older technology that's already obsolete and being superseded? Why are we buying a supposedly "fifth generation" warplane designed to defeat "fourth generation" warplanes and technologies? Shouldn't we be getting a fifth generation warplane that's going to be able to hold its own against newer, fifth generation warplanes fielding fifth generation weapons?
With the F-35 still years away from becoming operational, the United States and other countries are racing to develop new sensor technologies of the very sort you would want to use against F-35 vintage stealth.
"Multiple electro-optical sensors: long-wave infrared, mid-wave infrared, short-wave infrared, visible/near-infrared monochrome and colour/low-light television" systems. You can miniaturize some of this stuff and load it into drones that can communicate with your warplanes. Since the F-35 carries just two air to air missiles, you can force it to take out drones, and then move in for the kill. All you have to do is make it maneuver defensively and its stealth cloaking is gone.
And to keep your warplanes alive until they can close on the attackers, the players are developing DRFM (digital radio-frequency memory) chips, "that can intercept, record and mimic incoming radar signals rapidly and accurately, providing very effective jamming." The Euros and the Russians are leading on the DRFM technology.
Then there's another Russian specialty that's catching on with the Americans, IRST, or infrared search and tracking. They're supposedly getting near the range of radar systems which means well beyond visible range. Couple that with recent developments in passive radar tracking to cue the IRST and you've got a pretty accurate, long range system that doesn't care if you're in a stealth fighter or not. The Swedes, meanwhile, have a new data link system that provides a quiet and effective, air-to-air attack capability requiring two or more fighters operating their radars in passive mode.
And, in case you're in the mood for a little war porn, here's a SAAB promo vid.