Maybe some day.
Maybe some day.
Related: there is also a CSS property coming which allows sites to control which page content should be clamped to standard range or not. Worst case you can just add an * !important override in your Safari->Preferences->Advanced->Style Sheet if nobody else considers it problematic but you still wanted to clamp things (in Safari, otherwise you can just disable HDR).
The only reason Safari lacks HDR image support on macOS right now is it's their lowest priority platform for the feature. It's coming, it's supported on their other platforms, and it wasn't an unreviewed accident they've been working on it.