I always assume the worst! There will be some auto engineer trying to backport some functionality and will be googling "JSON Assembly" and will port this code.
It won't and should not be used in mission-critical applications, but just for extra fun, one may still want it to be as correct as possible. Right now I'm writing a cryptography library in PDP-11 assembly while investigating tools for its formal verification. Cryptoline looks like a promising candidate.
Never underestimate the longevity of systems, since new systems tend to be built on top of old systems.
Though I do not know any, I'm pretty sure in 2021 there *are* mission/security-critical applications running on 6502s in a number of places in the world.
The 6502 is one of the few processors validated for embedded medical devices. From https://www.westerndesigncenter.com/
".. the 65xx microprocessors protect millions of lives annually within embedded heart defibrillation and pacing systems. "
Can't get more mission-critical than that I suppose..