Greyelf is spot on. There are things which can be done to help mitigate potential issues—e.g., aggressive feature testing—but ultimately the balance of power rests in the hands of the various standards committees and browser manufacturers. Thus, if they decide to make significant changes to how parts of the various web technologies work, which could include breakage, then there’s not much people using the technology can do about it—aside grin and bear it.
Depending on the scale of the change, the fallout could range from: largely unnoticeable, a minor annoyance, demanding a workaround/rewrite either of the author’s code or, worse, the story format itself—anecdote follows.
Here’s a very relevant anecdote from 2015 that bit story formats themselves right in the keister, which some may recall.
Prior to Aug/Sep 2015, most of the then current story formats provided access to their history controls by integrating them with browser’s built-in history controls via the History API. Players were generally happy with that setup and things were good. Then Chrome 45 rolled out and things got ugly.
With that release, the Chrome developers attempted to reduce the risk of certain types of spoofing/phishing attacks by excluding blob and filesystem URLs from being allowed with the ‘self’ source defined by Content Security Policy directives. As one consequence of that change, locally opened files—the aforementioned filesystem URLs; i.e., those opened via file://—would no longer be allowed to use the History API in Chrome—quite possibly any Chromium-/Blink-based browser.
The fallout was that then current story formats were suddenly broken in the affected browsers for local play—the API would simply throw an exception, crashing the game. The end result of that fiasco was that story formats largely abandoned the History API and moved their history controls completely into their own UIs, separate from the browser’s.
It caused quite the gnashing of teeth among players, authors, and story format developers at the time—players and authors because suddenly their games stopped working, story format developers because we had to rewrite a core chunk of our story formats.
In fairness, that sort of apocalyptic change is extremely rare, so no one should be overly concerned—the sky is not falling. I’ve regaled you with the anecdote simply to reiterate Greyelf’s point that there’s no simple solution, for anyone, to the looming issue of future technology changes breaking existing code.