Seems reasonable, all else being equal, the party that is detected last has a higher chance of winning.
What happens when a new detection method is developed that makes these planes not stealthy? Don't you then just have 4-5th gen craft that cost 2-10x as much?
Guess it takes a real war to discover the actual winner of modern warfare.
You can be assured that Russia and China are working hard on technology to detect stealth planes (e.g. multistatic radar systems). But again, it's not a binary thing. Even with a multistatic radar setup, a stealth aircraft will have lower detection range than a non-stealthy one. And considering both China and Russia are developing stealthy aircraft like Su-57 and J-20, it seems they themselves are not thinking that they have the magic technology that would make stealth obsolete.
Can that be what 'stealth' means? Sensing technology must be progressing faster than the ability to remain off-radar. Between satellites, internet connected mobiles and general improvements in radar technology I'm not sure that a stealth aircraft can be undetected.
Also, stealth should never work alone, it should work in coordination with non-stealth aircraft, drones and stand off jammers as a coherent whole. Detecting stealth aircraft is easy, detecting stealth aircraft against massive background noise from a wall of jammers while missiles and drones are going after your radars is a lot harder.
There's no hiding in space, US, Russia and China have all demonstrated abilities to destroy satellites. In a significant war between any of those three nations those satellites will be gone in a week, maybe even a day.